Services FAQ's > Legionella Services
Q. What is Legionnaires' disease?
A. Legionnaires' disease is a type of pneumonia that
is caused by Legionella, a bacterium found primarily in
warm water environments. Both the disease and the bacterium
were discovered following an outbreak traced to a 1976
American Legion convention in Philadelphia. Pontiac fever,
a flu-like illness, is also caused by Legionella organisms
(legionellae), but is not as serious as Legionnaires'
disease. Most people who get Pontiac fever recover within
five days, without having to be hospitalized.
Q. What are the symptoms of Legionnaires' disease?
A. Legionnaires' disease develops within 2 to 10 days
after exposure to legionellae. Initial symptoms may include
loss of energy, headache, nausea, aching muscles, high
fever (often exceeding 104°F), and chest pains. Later,
many bodily systems as well as the mind may be affected.
The disease eventually will cause death if the body’s
high fever and antibodies cannot defeat it. Victims who
survive may suffer permanent physical or mental impairment.
Q. Is Legionnaires disease common?
A. Legionnaires’ is not rare. It is perceived as
rare only because most cases are never detected, and not
all detected cases are reported to public health authorities.
Because underdiagnosis and under-reporting make incidence
of the disease difficult to estimate, figures have varied
widely. The (U.S.) Centers for Disease Control and Prevention
(CDC), Atlanta, has estimated that the disease infects
10,000 to 15,000 persons annually in the United States,
but others have estimated as many as 100,000 annual U.S.
cases.
Another reason that Legionnaires’ is falsely perceived
as rare is that when cases are detected, the public rarely
hears about them. Most cases—at least 65 to 80 percent
in the United States and the United Kingdom —occur
sporadically (one or two at a time). Thus, only a small
percentage of cases occur as part of the multicase outbreaks
that sometimes make the news. Cases of the disease are
seldom publicized even when lawsuits are involved, because
most Legionnaires’ lawsuits are settled quickly
and under terms of confidentiality.
A case of Legionnaires’ disease will go undetected
unless special laboratory tests are performed. Unfortunately,
most U.S. hospitals still have not made these tests routinely
available. It is reasonable to assume that undetected
cases of Legionnaires’ are occurring because experience
has shown that increased suspicion of the disease among
physicians, when combined with increased patient testing,
leads to more diagnoses. Some hospitals have recognized
cases of Legionnaires’ disease only after increased
testing of patients with pneumonia. Likewise, in hospitals
where only one to three cases of Legionnaires’ were
identified over several months, numerous additional cases
were recognized after surveillance was intensified.
Studies of community-acquired pneumonia (cases acquired
outside hospitals) have also indicated that increased
surveillance leads to more diagnoses. A large-scale study
in Ohio (U.S.A.) suggested that only 3 percent of sporadic
cases of Legionnaires’ disease were correctly diagnosed.
By comparison, in studies in which diagnostic tests have
been consistently used, Legionella has been recognized
among the top three or four microbial causes of community-acquired
pneumonia.
Because the symptoms of Legionnaires’ are similar
to those of other types of pneumonia, undetected cases
of Legionnaires’ disease end up being classified
merely as pneumonia with no apparent cause. Based on CDC
estimates, this means that 8 to 39 pneumonia deaths occur
each week in the United States without anyone knowing
that the cause was Legionella. What’s worse is that
many of these deaths could be prevented because, unlike
most pneumonias, the source (e.g., a hot-water system)
of Legionnaires’ cases can be identified. But if
Legionella is not recognized as the cause, no investigation
ensues to pinpoint and disinfect the source, so the same
source remains a threat.
Q. How is Legionnaires' disease treated?
A. Erythromycin and Azithromycin, antibiotics, have been
effective, especially when cases are detected early.
Q. How does a person get Legionnaires' disease?
A. Legionnaires' disease is contracted by inhaling airborne
water droplets containing legionellae. Some investigators
believe that the disease may be acquired also by drinking
legionellae-contaminated water, particularly if legionellae
aspirated from the water are inhaled before the water
enters the stomach. Cases have also been blamed on contact
between contaminated water and incisions or skin wounds.The
disease is not contagious.
Q. Who is at risk of contracting Legionnaires
disease?
A. The risk of infection is based on two key factors:
the number of legionellae reaching the body and the resistance
of the individual. Young and healthy people can get Legionnaires’
disease, but persons who are immunocompromised either
because of illness (e.g., cancer) or medical treatment
(e.g., chemotherapy) are at a much higher risk because
they can be infected by relatively low legionellae counts.
HIV-infected patients, for example, have a 40-fold increased
risk; organ transplant recipients have a 200-fold increased
risk. Smokers, persons over 65 years of age, and heavy
drinkers have a moderately higher risk.
Children have contracted Legionnaires' disease. Most cases
have occurred in immunosuppressed children, but a number
of immunocompetent children, particularly newborns, have
acquired the disease, most often after surgeries, or through
the use of legionellae-contaminated ventilators. _
Q. What is the death rate?
A. Underlying disease and advanced age not only increase
the risk of contracting Legionnaires’ disease but
also the risk of dying from it, so it is not surprising
that a CDC study of reported cases indicated a death rate
of 40 percent for cases acquired during a hospital stay
(nosocomial cases), but a death rate of 20 percent for
community-acquired cases. Some outbreaks have claimed
more than 50 percent. _
Q. Can the risk of Legionnaires' Disease be determined
by geographical location?
A. No. Legionnaires’ disease is not specific only
to certain areas. Although some areas have reported more
cases of LD than other areas, the geographic location
is relatively insignificant. What’s more, the number
of cases reported from a given area could indicate the
level of awareness among physicians and the availability
of laboratory testing, as opposed to the level of legionellae
in the water supply. Legionella contamination is usually
tied to the condition of a building’s mechanical
system, which is independent of geographical location.
Q. What is the size of Legionella organisms?
A. The average Legionella cell is 0.5-1.0 micrometer
wide and 1.0-3.0 micrometers long (Barbaree, J. M. "Controlling
Legionella in Cooling Towers," ASHRAE Journal, June
1991; 38-42 _
Q. What are the long term side effects of Legionnaires
disease? I heard asthma is one side effect.
A. As with any acute illness, patients who recover from
Legionnaires' disease can suffer long term side effects.
The most common are fatigue and lack of energy for several
months. However, asthma of new onset is uncommon, although
I know of a few cases who have persistent chest x-ray
abnormalities with sustained wheezing. It is unclear as
to whether this can be blamed solely on Legionnaires'
disease; asthma may be due to a number of stresses besides
Legionnaires' disease. Answer provided by Victor L. Yu,
MD, Professor of Medicine, Unviersity of Pittsburgh; Chief,
Infectious Disease Section, VA Medical Center, Pittsburgh,
PA, USA.
Q. I have had Legionnaire's disease and been
treated with large doses of erythromycin. The disease
nearly killed me. My temperature was 107 degrees F; I
was at death's door. Luckily, I had a physician who stayed
by my side for days and suspected Legionnaire's. After
having a near-death experience, I want to make sure that
this never happens to me or any of my loved ones again.
Is there any chance that the bacteria are still in my
system, remaining a threat? Deborah Newman
A. I am sorry that you had such a punishing experience
with Legionnaires' disease (LD) , but I am also thankful
that you survived since the mortality can be high. The
answer to your question has only been clearly elucidated
in the last decade. In 1978, when I saw my first case,
we wondered if this could occur and our blood antibody
tests suggested that it might have occurred in two patients.
But, more complete studies with newer and more powerful
lab tests have shown that once you are cured with antibiotics,
the bacteria are cleared. So, you do not have to worry
about this. We have data on the largest collection of
patients with LD in the world and have followed them for
many years. Somewhat to our surprise, virtually none of
them have become reinfected. Apparently, they developed
immunity with their first infection. It appears that you
have some residual protection if you contract Legionnaire's
disease; however, the most effective method of prevention
is stopping cigarette smoking. Smokers are much more likely
to contract LD (as they are to contract other respiratory
infections including the flu). Fever exceeding 104.5 is
a hallmark of LD, so you should thank your MD for making
that fine diagnosis. Answer provided by Victor L. Yu,
MD, Professor of Medicine, Unviersity of Pittsburgh; Chief,
Infectious Disease Section, VA Medical Center, Pittsburgh,
PA, USA.
Q. I have a friend who has been diagnosed with
Legionnaires disease and is in the critical care department
of a local hospital. Is this a disease that is mandated
to be reported to the (U.S.) CDC? Will there be follow
up on the source of the bacteria?
A. In the United States, Legionaires' disease is a reportable
disease by law to the local public health department and
the CDC. Most health departments will not do a follow-up
unless many patients contract the illness. Answer provided
by Victor L. Yu, MD, Professor of Medicine, Unviersity
of Pittsburgh; Chief, Infectious Disease Section, VA Medical
Center, Pittsburgh, PA, USA.
Q. What can I do to make my home less conducive
to Legionella contamination?
A. The plumbing system (via showers and faucets), whirlpool
spas and bathtubs, and humidifiers present a potential
risk of legionellae exposure in homes. A number of measures
can be taken to minimize legionellae growth. The long
list of risk reduction options for homes cannot be covered
in this brief FAQ.
Q. Are certain types of buildings more prone
than others to have problems with legionellae?
A. Cases of Legionnaires' disease have been linked to
many types of equipment that contain water, but plumbing
systems and air conditioning systems are most often blamed.
Although it is possible to contract the illness from legionellae
growing in home plumbing systems, most cases have been
traced to large buildings. This may be because larger
piping networks are generally more conducive to legionellae
growth. Also, the air conditioning systems for large buildings
often include cooling towers, which contain a pool of
warm water in which legionellae can flourish.
Q. What precautions can be taken to prevent Legionnaires'
disease?
A. Legionnaires' is considered an environmental disease
because its causative agent (legionellae) is transmitted
from an environmental source (water) to a person (in contrast
with communicable diseases, such as AIDS, which are transmitted
from person to person). Therefore, keeping legionellae
out of water is the key to preventing the disease. For
example, plumbing systems can be maintained to minimize
the growth of legionellae. And if preventive measures
alone do not control the bacteria, disinfection procedures
can be implemented.
Q. How can I reduce my risk of getting Legionnaires'
disease?
A. You can reduce your risk of Legionnaires’ disease
by (a) lowering your susceptibility to infection and (b)
avoiding exposure to Legionella bacteria. The most important
factor in lowering your susceptibility to infection is
to stop smoking. Among persons who are not immunocompromised,
smoking is the number one factor in acquiring Legionnaires
disease. A study of 146 adults with Legionnaires’
disease indicated that smoking sharply increased the risk
of contracting the disease. As for avoiding exposure to
legionellae, you have several options. Some measures cost
nothing and should be implemented out of good sense. Expensive
measures could be a waste of money for healthy nonsmoking
adults, who are at low risk of contracting Legionaires
disease. High-risk individuals, however, should consider
taking every reasonable precaution.
Q. What precautions should be taken in working
on cooling towers?
A. Experts recommend wearing a high-efficiency particulate
air (HEPA) protective mask while cleaning cooling towers
or collecting samples from them, unless the tower fans
are shut off, especially if legionellae contamination
is suspected or hyperchlorination is in process. Full
masks allow less leakage and thus filter more than half
masks. A good fit is critical with any mask. Be aware,
however, that HEPA filters will not block all bacteria.
Gloves, goggles, and other body coverings have also been
suggested for cooling tower work.
Legionellosis is a common name for one of the several
illnesses caused by Legionnaires' disease bacteria (LDB).
Legionnaires' disease is an infection of the lungs that
is a form of pneumonia. A person can develop Legionnaires'
disease by inhaling water mist contaminated with LDB.
LDB are widely present at low levels in the environment:
in lakes, streams, and ponds.
At low levels of contamination, the chance of getting
Legionnaires' disease from a water source is very slight.
The problem arises when high concentrations of the organism
grow in water systems. Water heaters, cooling towers,
and warm, stagnant water can provide ideal conditions
for the growth of the organism.
Scientists have learned much about the disease and about
LDB since it was first discovered in 1976. The following
questions and answers will help you learn more of what
is currently known about Legionnaires' disease.
Q. What are the symptoms of Legionnaires' disease?
A. Early symptoms of the illness are much like the flu.
After a short time (in some cases a day or two), more
severe pneumonia-like symptoms may appear. Not all individuals
with Legionnaires' disease experience the same symptoms.
Some may have only flu-like symptoms, but to others the
disease can be fatal.
Early flu-like symptoms:
Slight fever
Headache
. Aching joints and muscles
. Lack of energy, tiredness
. Loss of appetite
Common pneumonia-like symptoms:
. High fever (102° to 105°F, or 39° to 41°C)
. Cough (dry at first, later producing phlegm)
. Difficulty in breathing or shortness of breath
. Chills
. Chest pains
Q. How common is Legionnaires' disease?
A. It is estimated that in the United States there are
between 10,000 and 50,000 cases each year. Most of them
sporadic cases not associate with outbreaks.Q. How does
a person get Legionnaires' disease?
A. A person must be exposed to water contaminated with
LDB. This exposure may happen by inhaling aerosolized
LDB or drinking water contaminated with LDB. Aspiration
may occur when choking or spontaneously during the drinking,
ingesting, swallowing process and allows oral fluids or
particles to by-pass natural gag relaxes and enter into
the respiratory tract and lungs instead of the esophagus
and stomach.Q. How soon after being exposed will a person
develop symptoms of the disease?
A. If infection occurs, disease symptoms usually appear
within 2 to 10 days.Q. Are some people at a higher risk
of developing Legionnaires' disease?
A. Yes, some people have lower resistance to disease and
are more likely to develop Legionnaires' disease.
Some of the factors that can increase the risk of getting
the disease include:
. Organ transplants (kidney, heart, etc.)
. Age (older persons are more likely to get disease)
. Heavy smoking
. Weakened immune system (cancer patients, HIV-infected
individuals)
. Underlying medical problem (respiratory disease, diabetes,
cancer, renal dialysis, etc.)
. Certain drug therapies (corticosteroids)
. Heavy consumption of alcoholic beverages
Q. Is Legionnaires' disease spread from person
to person?
A. To date, there is no evidence in the literature that
shows the spread of the disease from person-to-person
contact.
Q. What causes Legionnaires disease?
A. Legionnaires' disease most often is caused by inhaling
water contaminated with rod-shaped bacteria called Legionella
pneumophila. There are over 30 different species of Legionella,
many of which can cause disease. Legionella pneumophila
is the most common species that causes disease.
Q. Does everyone who inhales LDB into the lungs
develop Legionnaires' disease?
A. No. Most people have resistance to the disease. In
outbreaks, fewer than 5 out of 100 people exposed to water
contaminated with LDB typically develop Legionnaires'
disease.
Q. Is Legionnaires' disease easy to diagnose?
A. No. The pneumonia caused by LDB is not easy to distinguish
from other forms of pneumonia. A number of diagnostic
tests allow a physician to identify the disease. These
tests can be performed on a sample of sputum, lung tissue
collected by biopsy, blood, or urine.
Q. How is Legionnaires' disease treated?
A. Early treatment reduces the severity and improves
chances for recovery. The drugs of choice belong to a
class of antibiotics called macrolides. They include azithromycin,
erythromycin, and clarithromycin. In many instances physicians
may prescribe antibiotics before determining that the
illness is Legionnaires' disease because macrolides are
effective in treating a number of types of pneumonia.
Q. How did Legionnaires' disease get its name?
A. Legionnaires' disease got its name from the first
outbreak in which the organism was identified as the cause.
This outbreak occurred in 1976, in a Philadelphia hotel
where the Pennsylvania American Legion was having a convention.
Over 200 Legionnaires and visitors at this convention
developed pneumonia, and some died. From lung tissue,
a newly discovered bacterium was found to be the cause
of the pneumonia and was named Legionella pneumophila.
Q. Is Legionnaire's disease a new disease?
A. No. Legionnaires' disease was first recognized in
1976. Unsolved pneumonia outbreaks that occurred before
then are now known to have been Legionnaires' disease.
One year later, CDC identified the causative agents (species
of LDB). Scientists are still studying this disease to
learn more about it.
Q. Are LDB widespread in the environment?
A. Yes, studies have shown that these bacteria can be
found in both natural and manmade water systems. Natural
water sources including streams, rivers, freshwater ponds
and lakes, and mud can contain the organism in low levels.
Q. Could I get the disease from natural water
sources?
A. It is unlikely. In the natural environment the very
low levels of this organism in water probably cannot cause
disease.
Q. What water conditions are best for growth
of the organism?
A. Warm, stagnant water provides ideal conditions for
growth. At temperatures between 20°C-50°C (68°-122°F)
the organism can multiply. Temperatures of 32°C-40°C
(90°-105°F) are ideal for growth. Rust (iron),
scale, and the presence of other microorganisms can also
promote the growth of LDB.
Q. What common types of water are of greatest
concern?
A. Water mist from cooling towers or evaporative condensers,
evaporative coolers (swamp coolers), humidifiers, misters,
showers, faucets, and whirlpool baths can be contaminated
with LDB and if inhaled or aspirated into the lungs can
cause the disease.
Q. Can Legionnaires' disease be prevented?
A. Yes. Avoiding water conditions that allow the organism
to grow to high levels is the best means of prevention.
Specific preventive steps include:
. Regularly maintain and clean cooling towers and evaporative
condensers to prevent growth of LDB. This should include
twice-yearly cleaning and periodic use of chlorine or
other effective biocide.
. Maintain domestic water heaters at 60°C (140°F).
The temperature of the water should be 50°C (122°F)
or higher at the faucet.
. Avoid conditions that allow water to stagnate. Large
water-storage tanks exposed to sunlight can produce warm
conditions favorable to high levels of LDB. Frequent flushing
of unused water lines will help alleviate stagnation.
Q. Do you recommend that I operate my home water
heater at 60°C (140°F)?
A. Probably not if you have small children or infirm
elderly persons who could be at serious risk of being
scalded by the hot water. However, if you have people
living with you who are at high risk of contracting the
disease, then operating the water heater at a minimum
temperature of 60°C (140°F) is probably a good
idea. Consider installing a scald-prevention device.
Q. What can be done if a water system is already
contaminated or is suspected of being contaminated?
A. Special cleaning procedures and water treatment can
reduce LDB in water systems. In many cases, these procedures
involve the use of chlorine-producing chemicals or high
water temperatures. Seek professional assistance before
attempting to clean a contaminated water system.
Q. Can my home water heater also be a source
of LDB contamination?
A. Yes, but evidence indicates that smaller water systems
such as those used in homes are not as likely to be infected
with LDB as larger systems in workplaces and public buildings.
Q. Can LDB cause other diseases?
A. Yes. In addition to Legionnaires' disease, the same
bacteria also can cause a flu-like disease called Pontiac
fever.
Q. How does Pontiac fever differ from Legionnaires'
disease?
A. Unlike Legionnaires disease, which can be a serious
and deadly form of pneumonia, Pontiac fever produces flu-like
symptoms that may include fever, headache, tiredness,
loss of appetite, muscle and joint pain, chills, nausea,
and a dry cough. Full recovery occurs in 2 to 5 days without
antibiotics. No deaths have been reported from Pontiac
fever.
Q. Are there other differences between Legionnaires'
disease and Pontiac fever?
A. Yes. Unlike Legionnaires' disease, which occurs in
only a small percentage of people who are exposed, Pontiac
fever will occur in approximately 90 percent of those
exposed. In addition, the time between exposure to the
organism and appearance of the disease (called the incubation
period) is generally shorter for Pontiac fever than for
Legionnaires' disease. Symptoms of Pontiac fever can appear
within one to three days after exposure. Pontiac fever
has been associated with exposure to non-viable LDB and
may be a hypersensitivity response to bacterial or other
antigens rather than an infection.Case studies
Murcia Spain outbreak This LD outbreak is the largest
to date in the world, with 449 confirmed cases and an
estimated total number of cases of 650. The reported case-fatality
rate (1%) is much lower than those observed in other community
outbreaks.This rate can be attributed, at least partially,
to the quick detection of the outbreak, early diagnosis
of the disease, and appropriate treatment of patients.
The explosive quality of the outbreak not only led patients
to seek quick assistance at hospital emergency units but
also helped clinicians to perform an accurate diagnosis
and to immediately initiate adequate treatment, factors
reported as linked to low case fatality.This explosive
appearance could also be related to a lower presence of
predisposing factors in case-patients in comparison with
other community outbreaks,[which could also partially
explain the low case-fatality rate.
The initial investigation encountered obstacles, such
as a large number of potential sources of environmental
contamination located in the northern part of the city
and the absence of environmental Legionella isolates identical
to those of patients. The case-control study showed a
significant association, with a high consistency between
the analyzed models and with a high magnitude of association,
between passing through the zone around hospital H and
being ill with LD. Results were similar even when the
area radius was expanded to 400 m. However, large overlap
of areas was observed within this radius, and multicollinearity
among zones was a common finding.
The case-control study was designed to select patients
residing outside the city of Murcia. We decided on this
approach for two reasons. First, the incidence of LD was
almost 1% in some neighborhoods, a rate within the 0.1%
to 5% attack rate described for this disease. Therefore,
all the persons living in these quarters could possibly
have been exposed to Legionella, as has been described
in outbreaks of other transmissible diseases. If everyone
had been exposed, finding incidence differences between
persons exposed and those not exposed would have been
almost impossible. Second, persons residing outside the
city would probably have a more accurate memory of the
itineraries they followed in Murcia some weeks previously
and would probably have a lesser number of routes than
persons living within the city. Conducting 255 personal
interviews with questions about itineraries within 2 weeks
from the last case and 4 weeks from the outbreak onset
may also have been important to our findings.
One concern in case-control studies is that participation
rate is not reported consistently. Indeed, this information
is usually omitted in case-control studies of outbreaks,
especially when controls are selected from a population
database, as was our situation. A further complication
was that the study had to be conducted in July, when many
people go on holiday. In spite of achieving the participation
of one in two controls whom we initially selected, we
evaluated possible selection bias. We determined that
it was unlikely to have occurred since neither socioeconomic
status nor predisposing risk factors for LD differed significantly
among cases and controls. Information bias overestimating
this outcome was ruled out since news media did not mention
hospital H among the probable sources of the outbreak.
Meteorologic conditions were favorable for the emission
of aerosols to be dispersed in a horizontal manner. Low
wind speed together with atmospheric thermal inversion
between June 29 and July 1 would have facilitated the
presence of the aerosols in the environment.
The result of the epidemiologic study was subsequently
confirmed by the isolation of a strain retrieved on October
30 from a sample from one of the cooling towers of the
same hospital; that strain is identical to the strain
isolated from the patients. The difficulties found previously
in the isolation of this strain were not unexpected. The
day after the outbreak was detected, when the first sample
was taken, the cooling towers of hospital H were highly
chlorinated, which could explain why these first samples
gave negative results. Later samples retrieved on four
different dates between July 28 and September 13 showed
positive results to L. pneumophila but were characterized
as different strains from those from patients. This strain
was only isolated upon the restarting of one tower after
it was shut down for more than 1 month, a condition that
favors the reappearance of Legionella.The fact that the
same clone of Legionella can be found in an installation
for long periods is also documented.The possible contamination
of the tower by new Legionella from the water supply was
ruled out since the strain linked to the outbreak was
not found in samples collected from many other installations
during the same period, including July to November.
The coincidence of a nosocomial LD outbreak in hospital
H reinforces the previous hypothesis. A nosocomial outbreak
of LD as part of a wider community outbreak of the disease
has been described, although in other outbreaks originating
in the cooling towers of a hospital no cases of nosocomial
LD were identified.The use of double HEPA filters on air-intake
vents in some hospitals could justify, at least in part,
these contradictory observations.
Our research indicates that the cooling towers of a hospital
located in the northeastern part of the city of Murcia
were the origin of this community outbreak. This study
underlines important risk factors that must be taken into
account to prevent a new LD outbreak. First, cooling towers
had to be identified by aerial and direct inspection in
the absence of any census of such installations. Second,
the size, location, and state of maintenance of cooling
towers are very important. In contrast with epidemics
associated with relatively small systems, this outbreak
was related to a large refrigeration system that seems
to have infected patients up to 1.3 km downwind to the
west from the cooling tower; this finding suggests that
airborne infection with L. pneumophila may extend over
a large distance from the dissemination source, as has
been reported elsewhere. Although most of the installations
in the area showed inadequate maintenance, the cooling
towers from hospital H were poorly maintained and had
a high-risk size and location. Once the outbreak was identified,
urgent measures were undertaken to clean, disinfect, or
close possibly contaminated sources. The cooling tower
that was the source of the outbreak was subsequently replaced
by an air-cooled system.
Before June 2001, no specific national legislation existed
in Spain concerning LD, although a recommendation guide
and legislation existed in several Spanish autonomous
regions that had had community LD outbreaks. As an immediate
consequence of this outbreak, a national law about prevention
and control of LD was enacted in Spain 20 days after the
outbreak began. The extent of this outbreak is useful
to assess the relative role of cooling towers as a source
of LD and highlights the importance of prioritizing control
measures related to cooling towers among strategies to
prevent LD in the community. Compliance with these measures
would help to reduce not only community outbreaks but
also, perhaps, sporadic cases that could be due to infected
cooling towers.
Cruise ship outbreak May 2003
More than 9.4 million passengers traveled on pleasure
cruises departing from North American ports in 2004, an
increase of 13% since 2003 and 41% since 2001.1 Cruise
ships typically transport closed populations of thousands
of persons, often from diverse parts of the world. Travelers
are at risk for becoming ill while on board, most commonly
from person-to-person spread of viral gastrointestinal
illnesses. Certain environmental organisms, such as Legionella
spp., pose a risk to vulnerable passengers. During November
2003–May 2004, eight cases of Legionnaires disease
(LD) among persons who had recently traveled on cruise
ships were reported to CDC. This report describes these
cases to raise clinician awareness of the potential for
cruise-ship–associated LD and to emphasize the need
for identification and reporting of cases to facilitate
investigation.
LD is a severe community– or health-care–associated
pneumonia caused by Legionella spp., most commonly L.
pneumophila. LD can result from inhalation or aspiration
of warm (25°C–42°C), aerosolized water containing
Legionella. Symptoms typically begin 2-10 days after exposure.
Person-to-person transmission does not occur. Because
symptoms of LD (e.g., fever, cough, or chest pain) are
nonspecific, LD cannot be reliably distinguished from
other forms of pneumonia on the basis of clinical presentation
alone.
In the United States, LD can be reported to CDC through
two surveillance systems. The National Electronic Telecommunications
System for Surveillance collects information on all reportable
diseases from state and territorial health departments
but does not collect information on travel history. In
contrast, the paper-based Legionnaires Disease Reporting
System collects details of any recent travel from LD patients
but receives data on only a fraction of the total cases
estimated to occur. The cases described in this report
were initially relayed to CDC by direct communication
from state health departments, cruise lines, and the European
Working Group for Legionella Infections (EWGLI), which
operates a surveillance scheme (EWGLINET) for LD among
European travelers (http://www.ewgli.org). Cases were
defined as laboratory-confirmed LD in a person with cruise-ship
travel during the 10 days before symptom onset. Exposure
history was collected by the state and local health departments,
and environmental samples, when obtained, were tested
by contractors hired by the cruise lines.
The eight cases were among passengers who had been aboard
five different cruise ships and associated with seven
different voyages. Two of the eight cases occurred on
the same voyage. The mean age of the patients was 55.8
years (range: 23-76 years). Five (63%) were male; seven
(88%) were U.S. residents. The sole case in a foreign
traveler occurred in a Dutch woman aged 23 years who had
onset of fever and cough 4 days after returning from a
cruise in the Caribbean. Two (25%) cases were fatal. Of
the seven patients with known medical histories, six (86%)
had comorbidities or risk behaviors known to be risk factors
for LD (e.g., diabetes, history of heart disease, or smoking).
The mean time from cruise-ship boarding to onset of symptoms
was 10.4 days (range: 4-16 days). Although two passengers
had symptoms before the end of their respective cruises,
only one had LD diagnosed while still aboard the ship.
Seven (88%) were diagnosed by urinary antigen testing
for Legionella pneumophila serogroup 1 (Lp1). The only
person with LD diagnosed by a fourfold increase in anti-Legionella
spp. serology had a negative Legionella urinary antigen
test. Only the Dutch traveler had a culture for Legionella
obtained at the onset of illness. The culture was positive
for Lp1; a urinary antigen test also was positive.
Two cases occurred on each of three cruise ships. Two
patients were aboard the same ship during the same period
but had been friends preceding the cruise and therefore
had other exposures in common. A definite source of exposure
could not be identified for any of the cases because of
the limited number of cases. In addition, all but one
patient lacked a clinical isolate, limiting the ability
to link clinical and environmental isolates. For the Dutch
passenger, the sole patient with a clinical isolate, environmental
sampling was performed, but no matching environmental
isolate was identified. Additional case-finding measures
included review of infirmary records by cruise lines and
CDC, passive surveillance by cruise lines, public health
alerts via the Epidemic Information Exchange (Epi-X),
and notifications to EWGLI in the event vacationing European
travelers had become ill. Despite these activities, no
other cases were identified.
Reported by:
_C Joseph, DrPH, EWGLINET, London, England. J van Wijngaarden,
MD, Dutch Ministry of Health, Welfare, and Sport. P Mshar,
MPH, Connecticut Dept of Health. C Oravetz, Flagler County
Health Dept, Bunnell, Florida; AM Fix, MPH, Florida Dept
of Health. CA Genese, MBA, New Jersey Dept of Health and
Senior Svcs. GS Johnson, M Kacica, MD, New York State
Dept of Health. B Weant, Guilford County Dept of Public
Health, Greensboro, North Carolina; P Jenkins, EdD, North
Carolina Dept of Health and Human Svcs. N Baker, MPH,
Philadelphia Dept of Health. D Forney, J Ames, MPH, G
Vaughan, MPH, Jon Schnoor, Vessel Sanitation Program,
National Center for Environmental Health; D Kim, MD, M
Guerra, DVM, Div of Global Migration and Quarantine; B
Fields, PhD, M Moore, MD, Div of Bacterial and Mycotic
Diseases, National Center for Infectious Diseases; C Newbern,
PhD, M Thigpen, MD, EIS officers, CDC.
_CDC Editorial Note:
_During 1980-1998, CDC received an average of 360 paper-based
reports of LD annually, primarily during summer months.2
However, previous research using population-based active
surveillance estimated that 8,000-18,000 cases of Legionella
spp. infection requiring hospitalization occur in the
United States annually, suggesting that legionellosis
is underdiagnosed and/or underreported.3 Since the first
recognized outbreak of LD occurred in 1976 among persons
attending the American Legion convention in Philadelphia,
travel has been identified as a risk factor for both outbreak-associated4
and sporadic infection.5 However, for multiple reasons,
outbreaks of travel-associated legionellosis are difficult
to detect and investigate.6-7 First, trends toward empirical
use of antimicrobial agents have led to declines in diagnostic
testing for etiologic agents of community-acquired pneumonia.8
Second, the incubation period of 2-10 days allows travelers
to return home before they have symptoms, making it unlikely
for a medical provider to see more than a single case.
Third, because LD can be diagnosed within hours of specimen
collection by urine antigen testing, diagnosis by culture,
which requires several days, has declined substantially
in recent years.2
The lack of clinical isolates hinders epidemiologic investigations
and prevention strategies. Legionella spp. can be identified
by culture in up to 40% of freshwater environmental samples
and in up to 80% of environmental samples by polymerase
chain reaction.9 Although Lp1 causes approximately 70%
of cases, at least 22 species of Legionella have been
associated with disease in humans.9 To determine which
of many potential environmental Legionella spp. is the
causative organism, a clinical isolate from a respiratory
culture must be matched to the environmental isolate by
monoclonal antibody subtyping or by molecular methods.
For these reasons, when evaluating a patient with suspected
LD, clinicians should obtain a travel history and collect
respiratory secretions for culture, in addition to collecting
urine for antigen testing.
Reporting of LD is mandatory in every state. However,
dispersion of travelers to multiple states after an exposure
might result in a health department receiving only one
report in association with a particular ship or hotel.
Cruise-ship– associated travel poses additional
difficulties for notification and investigation of LD
cases. For cruise ships that sail in international waters,
patients might be hospitalized in other countries, delaying
or precluding reporting to authorities in the patients'
home countries. Because travelers often stay in hotels
before or after cruise-ship travel and often disembark
at various international ports of call during a cruise,
numerous potential sources exist for authorities to investigate.
In certain instances, cruise-ship travel might be of insufficient
duration (e.g., a single day or overnight trip) to be
inclusive of the 2-10-day incubation period of LD. In
addition, the limited number of reported cases associated
with cruises limits the ability of traditional epidemiologic
methods to identify a source. Thus, the task of identifying
a source often relies on matching a clinical isolate to
an environmental isolate. However, few cases have been
reported for which an environmental isolate identified
from a cruise ship (most often from a whirlpool spa) was
identical to a clinical isolate from an ill passenger.6-7
Obtaining a clinical isolate from a patient with travel-associated
LD is essential to identifying the source of infection.
Public health programs have focused on reducing the risk
for LD among cruise-ship passengers. In 1994, CDC investigated
an LD outbreak on board a cruise ship and subsequently
issued recommendations to reduce transmission of Legionella
spp. from shipboard whirlpool spas.10 In addition, CDC's
Vessel Sanitation Program regularly conducts inspections
of these spas and other environmental sources. Given the
difficulties in confirming cases of LD, cooperation of
clinicians and local, national, and international public
health agencies is essential to foster diagnosis and prevention.
Because a single case of LD in a traveler might indicate
an outbreak, prompt recognition and direct reporting to
local, state, and federal officials can prevent additional
cases of travel-associated illness.
_REFERENCES
_1. US Department of Transportation. Maritime Administration.
Data and statistics: cruise passenger statistics. Available
at http://www.marad.dot.gov/marad_statistics.
2. Benin AL, Benson RF, Besser RE. Trends in Legionnaires
disease, 1980-1998: declining mortality and new patterns
of diagnosis. Clin Infect Dis. 2002;35:1039-1046. FULL
TEXT | ISI | PUBMED
3. Marston BJ, Plouffe JF, File TM, et al. Incidence of
community-acquired pneumonia requiring hospitalization:
results of a population-based active surveillance study
in Ohio. Arch Intern Med. 1997;157:1709-1718. ABSTRACT
4. Fraser DW, Tsai TR, Orenstein W, et al. Legionnaires'
disease: description of an epidemic of pneumonia. N Engl
J Med. 1977;297:1189-1197. ABSTRACT
5. Straus WL, Plouffe JF, File TM, et al. Risk factors
for domestic acquisition of Legionnaires disease. Arch
Intern Med. 1996;156:1685-1692. ABSTRACT
6. Jernigan DB, Hofmann J, Cetron MS, et al. Outbreak
of Legionnaires' disease among cruise ship passengers
exposed to a contaminated whirlpool spa. Lancet. 1996;347:494-499.
FULL TEXT | ISI | PUBMED
7. Ricketts K, Joseph C, European Working Group for Legionella
Infections. Travel-associated Legionnaires' disease in
Europe: 2003. Euro Surveill. 2004;9:40-43. PUBMED
8. Bartlett JG. Decline in microbial studies for patients
with pulmonary infections. Clin Infect Dis. 2004;39:170-172.
FULL TEXT | ISI | PUBMED
9. Fields BS. Legionellae and Legionnaires' disease. In:
Hurst CJ, Crawford RL, Knudsen GR, McInerney MJ, Stetzenbach
LD, eds. Manual of environmental microbiology. 2nd Edition.
Washington, DC: ASM Press; 2001:666.
10. CDC. Final recommendations to minimize transmission
of Legionnaires' disease from whirlpool spas on cruise
ships. Atlanta, GA: US Department of Health and Human
Services, CDC; 1997.
_
Car plant workers in ohio 2001
During March 12-15, 2001, four cases of Legionnaires'
disease (LD) among workers at an automotive engine manufacturing
plant (plant X) were reported to the Cuyahoga County Board
of Health, Cleveland, Ohio; all four diagnoses were confirmed
by Legionella urine antigen. Illness onset among the four
workers occurred during March 2-4; two workers died. Beginning
March 14, CDC assisted state and local health departments
with an investigation to identify new cases and potential
sources of Legionella transmission in the plant. This
report summarizes the investigation; findings indicate
an epidemiologic association with exposure to one of the
plant finishing lines but did not identify a specific
source.
Plant X manufactures cast iron engine components, is operated
by approximately 2500 employees, and covers approximately
1.6 million square feet of floor space. The plant is divided
into four areas: core making, mold production, iron melting,
and finishing. A confirmed case of LD was defined as radiograph-confirmed
pneumonia and laboratory evidence of Legionella infection,
defined as a positive Legionella urine antigen or isolation
of Legionella from respiratory secretions or lung tissue.
Specimens from the four initial case-patients were sent
to CDC for isolation of Legionella; available specimens
included one sputum specimen, one broncho-alveolar lavage
specimen, and lung tissue from the two decedents. Active
LD surveillance was established in all hospitals in the
greater Cleveland area. Hospital records and plant X employee
absentee records were reviewed to identify additional
cases. An environmental investigation was conducted to
identify aerosol-producing water sources for Legionella
transmission, including cooling towers, water hoses, and
water heaters.
No additional confirmed LD cases were identified among
the workers. Nine workers from plant X were hospitalized
during February 14–March 28; four had pneumonia,
and all nine had negative Legionella urine antigen tests.
Legionella pneumophila, serogroup 1, was isolated from
a worker's sputum sample, which was stored at 40°F
(4°C) for greater than1 week before culture. Results
are pending from lung tissue samples. Legionella was isolated
from 18 (9%) of 197 environmental samples, and at least
five species were identified. Three samples grew L. pneumophila,
serogroup 1; none matched the clinical isolate by monoclonal
antibody staining.
A case-control study was conducted to determine risk factors
for exposure to Legionella among plant workers. A case-patient
was defined as a worker at plant X during February 14–March
28 who had either a confirmed case of LD or a possible
case of legionellosis. A possible case-patient of legionellosis
was defined as a worker with a titer of anti-legionella
IgG antibody 1:1024 and any two of the following symptoms:
cough, shortness of breath, fever, headache, myalgia,
or fatigue. Controls were randomly selected workers with
fewer than two symptoms and IgG antibody 1:64. Serologic
specimens were collected 4-5 weeks after the presumed
exposure. Each study participant was asked detailed questions
about time spent inside and outside of the plant and information
about underlying medical conditions associated with LD.
Among 855 workers who were contacted, 484 (57%) agreed
to participate in the case-control study; 11 met case
criteria (four confirmed and seven possible cases), and
105 met criteria for controls. Visiting one of the finishing
lines in the plant (odds ratio [OR] = 15.1; 95% confidence
interval [CI] = 3.0-76.2) and working in the finishing
region of the plant (OR = 3.8; CI = 1.0-13.8) were associated
with disease.
Plant X was closed during March 14-19 to facilitate environmental
sampling and decontamination. All water systems were decontaminated,
and ongoing environmental surveillance for Legionella
was implemented throughout the plant, including the finishing
area. Sources of aerosolized water from the finishing
area that had been sampled before decontamination did
not yield cultures positive for Legionella. On the basis
of the case-control study results, additional environmental
samples were collected in the finishing area on April
14; all samples were negative for Legionella. County health
officials are obtaining maintenance records from the implicated
area of plant X to determine how transmission might have
occurred.
_Reported by:
T Allan, T Horgan, H Scaife, Cuyahoga County Board of
Health, Cleveland; E Koch, S Nowicki, MK Parrish, E Salehi,
Ohio Dept of Health. Respiratory Diseases Br, Div of Bacterial
and Mycotic Diseases, National Center for Infectious Diseases;
Hazard Evaluations and Technical Assistance Br, Div of
Surveillance, Hazard Evaluations and Field Studies, National
Institute for Occupational Safety and Health; and EIS
officers, CDC.
_CDC Editorial Note:
Industrial plants can be a source for the propagation
and transmission of Legionella. The identification of
L. pneumophila in the environmental samples demonstrated
that legionellae can survive in this work environment.
The tightly clustered onset of illness, lack of other
epidemiologic associations among the four confirmed patients
besides working in plant X, and the results of the case-control
study implicated a particular finishing line within the
plant as the likely source of Legionella. The narrow period
of illness onset and the failure to identify new cases
among plant workers suggest that exposure to the infecting
Legionella strain was short-lived and transient, which
may explain the failure to find an environmental sample
that matched the clinical isolate.
LD outbreaks have been reported in industrial settings,
including an automotive plant where workers were exposed
to contaminated metal-working fluids,1 factories that
used water to cool molded plastics,2 and waste-water treatment
facilities.3 In each setting, an aerosol-producing device
was implicated. Guidelines to minimize the risk for Legionella
transmission in these sites are available.4 In addition
to LD, clinicians should consider hypersensitivity pneumonitis,
metal fume fever, and humidifier fever as possible diagnoses
of an acute febrile respiratory illness with systemic
symptoms in persons who work in an industrial setting.5
Legionella species are estimated to account for 2%-15%
of all community-acquired pneumonia; however, only 1200-1500
cases are reported annually.6,7 Appropriate diagnostic
testing for LD includes Legionella urine antigen and culture
of respiratory secretions. Legionella urine antigen tests
provide rapid and accurate diagnosis of disease caused
by L. pneumophila, serogroup 1; however, these tests do
not identify less common species or serogroups and do
not provide an isolate necessary to compare clinical with
environmental isolates during outbreak investigations.
LD also can be diagnosed by a four-fold rise in anti-legionella
antibody titer or by direct fluorescent antibody on sputum
samples, although the latter method lacks specificity
and sensitivity. In addition to testing for Legionella
urine antigen, the diagnosis and investigation of LD cases
would be improved if clinicians obtained respiratory specimens
for culture by a laboratory proficient in Legionella isolation.
To facilitate appropriate investigation and improve understanding
of disease associated with Legionella species, health-care
providers should report legionellosis cases to county
or state health departments, and state health departments
should report legionellosis cases to CDC.
History
In July 1976, the American Legion held a convention at
the Bellevue-Stratford Hotel in Philadelphia to celebrate
the country's bicentennial. Within two days after the
start of the event, one veteran after another became ill
with an acute pneumonia illness. Ultimately, 221 patients
were stricken, and 34 patients eventually died of this
mysterious epidemic which came to be known as Legionnaires'
Disease.
There was pandemonium once word hit Congress and the White
House because the government feared the epidemic to be
the beginning of an influenza pandemic known as the Swine
Flu, which was already racing through Asia. President
Ford was so frightened he even signed the National Swine
Flu Immunization Program of 1976, to ensure mass immunization
for all American citizens, however, the Swine Flu possibility
was soon excluded.
During the Fall of 1976, imaginations soared with proposed
etiologies from scientists, physicians, media personnel,
and the public. Theories ranged from nickel carbonyl intoxication
and viral pneumonia to communist or pharmaceutical company
conspiracies against the American veterans. The CDC investigation
soon expanded--all the disease survivors and their available
relatives, and over 4,400 Legionnaires and their families
were questioned, and cadavers were autopsied at the microscopic
level.
By September 1976, the focus of the investigation shifted
entirely to the Bellvue-Stratford Hotel. The CDC team
collected numerous samples from the air, water, soil,
dirt and materials from the hotel and its surroundings.
However, these samples tested negative for a questionable
microbe or toxic chemical. Finally, on January 18,1977,
it was announced that Joseph McDade and team isolated
the bacterium that causes Legionnaires' Disease. McDade
couldn't grow the bacteria for reasons to be discovered,
yet he succeeded in obtaining evidence of its existence
and pathogenesis through a series of experiments.
Further analysis revealed that the bacteria thrived in
the Bellevue-Stratford hotel's cooling tower. From that
water supply the hotel derived its air conditioning and
the bacteria were actively pumped into the hotel. Since
1976, air conditioning changed, with federal agencies
all over the world requiring more stringent cleaning and
hygiene provisions for cooling towers and large scale
air conditioning systems.
Initial Isolation of Causative Agent
The evidence for the existence and pathogenesis of the
bacteria that causes Legionnaires' Disease was first discovered
in January 1977, by Joseph McDade and team through a series
of experiments. The first step was to remove lung samples
from a deceased legionnaire. These cell were ground up,
injected into chicken eggs, and incubated. After the incubation
period, the eggs were cracked, and the yolk sacs were
extracted, ground up and injected into the foot pads of
guinea pigs. These animals then developed the typical
symptoms of Legionnaires' disease. McDade then drew blood
samples from disease survivors assuming that they contained
antibodies against the causative agent. He then mixed
the samples with the yolk sac isolates and they reacted!!
confirming that the agent in the yolk sacs was the same
agent that caused disease in those 33 people.
McDade went on to explain that his team had been stumped
for months by several unusual characteristics of the bacteria:
1)The bacteria wouldn't grow under typical conditions.
The scientists tried to culture bacteria from the legionnaires'
blood and tissue samples in solution filled with standard
media fluid used to grow other bacterial varieties, however,
nothing happened so they thought it as a virus.
Virologists then accidentally killed the bacteria by using
culture media with antibiotics in order to eliminate chance
of bacterial infection. It wasn't until they injected
samples not treated with antibiotics into the eggs that
they saw evidence that living organisms inhabited the
bodies.
2)Another stumbling block was the mice used in the lab
throughout the summer and fall. It wasn't until they switched
to guinea pigs that their efforts were productive. They
did not know the reasons for this, but as it turns out
in mammals, the bacteria only replicate inside macrophages
and other phagocytic cell. The growth of the bacteria
and subsequent spread of the disease therefore depends
on the ability of macrophages to ingest the bacteria.
Mice macrophages are very inefficient at ingesting this
bacteria, therefore, they never got infected from samples
from the legionnaires'.
The next step for McDade was to determine why this bacteria
was so difficult to culture. They soon discovered that
the legionella bacterium has peculiar dietary needs. Standard
culture media does not promote growth because it requires
high levels of the amino acid cysteine, inorganic iron
supplements, low sodium concentrations, and activated
charcoal. Also, the bacterium tend to live in a nutrient
rich, dark environment (among "pond scum"),
and in the cytoplasm of larger organisms. These conditions
contribute to the difficulty in viewing the organism using
standard molecular techniques. After treatment with silver,
however these organisms can be clearly seen.
Causative Agent
Since 1977, 41 species of Legionella species containing
62 serogroups have been characterized, 21 species are
associated with disease, while the others are environmental
isolates, whether these can cause disease is not yet known.
Legionella pneumophila is responsible for more than 80%
of Legionnaires' disease cases, and among the 13 serogroups,
serogroup 1 is responsible for 95% of these cases. It
is estimated that L. pneumophila is responsible for 25,000
cases of pneumonia a year, however, that number is probably
underestimated due to the difficulty in isolating and
culturing the bacteria. Since L.pneumophila is the most
frequent and pathogenic cause of Legionnaires' disease,
most studies focus on this particular species.
The bacteria are gram negative, non-acid fast, non-fermentative,
and aerobic. They are non-capsulated rods that range from
0.3-0.9 x 2-20 micrometers. They are difficult to culture
because they require increased levels of the amino acid
cysteine, inorganic iron supplements, decreased sodium
concentration, and activated charcoal.
The bacteria have 3 properties which are important with
regard to their control:
1)They are widely distributed at a low concentration.--These
bacteria are both naturally and artificially occurring.
Naturally they occur in surface water (streams, rivers,
lakes, ponds), and in moist soils. Artificially they occur
in evaporative cooling systems, domestic water systems,
air conditioning plants, ventilation systems, humidification
systems, shower heads, whirlpools and spas.
2)They flourish in water of various temperatures.--These
bacteria can survive in water temperatures between 25-45
degrees Celsius, however, they can survive in temperatures
up to 65 degrees Celsius. These warm temperatures also
support the growth of scale an algae which are utilized
by the bacteria for nutrients.
3)They cause disease only if inhaled.--Bacterial transmission
occurs to humans through droplets generated from environmental
sources and man-made devices that generate aerosols. Person
to Person transmission has never been documented.
In the environment Legionella species can't multiply extracellularly,
and have been shown to be parasites of protozoa-13 species
of amoebae and 2 species of protozoa that allow intracellular
bacterial replication have been shown to be potential
environmental hosts for legionella. It is an intriguing
discovery since most protozoan species feed on bacteria,
and legionella remain the only bacterial species that
are prolific in their intracellular replication within
amoebae. This sophisticated host parasite relationship
indicates a tremendous adaptation of legionella to parasitize
protozoa and amoebae.
Role of Protozoa in Legionnaires' Disease:
1)Many protozoan hosts, which are the only means of bacterial
amplification in the environment, have been identified.
2)In outbreaks of Legionnaires' disease, both amoebae
and bacteria have been isolated from the source of the
infection, the amoebae have later been shown to support
the intracellular replication of the bacteria in laboratory
cultures.
3)Following replication within protozoa, the bacteria
show a rise in resistance to harsh conditions including
high temperatures and acidity which may facilitate survival.
4)Bacteria within protozoa are more resistant to chemical
disinfection and biocides.
5)Protozoa release vesicles of respirable size that contain
numerous amounts of bacteria. Bacteria within these vesicles
are also more resistant to harsh conditions.
6)After protozoan release, bacteria show a dramatically
enhanced ability to infect mammalian cells. The number
of bacteria isolated from a source of infection of Legionnaires'
Disease is usually low and thus enhanced infectivity of
intracellular bacteria may compensate.
7)There are no documented cases of transmission between
individuals.
It is clear that the association of legionella with protozoa
is a major factor in the continuous presence of bacteria
in the environment.
TramissionTransmission, Infection, and Damage
TRANSMISSION
The legionella bacterium is inhaled and ingested in the
air space of the lungs by resident alveolar macrophages
which fail to kill or even inhibit the growth of the bacteria.
INFECTION
A little background about Phagocytosis: Phagocytic cells
recognize invading organisms with receptors on their surface
that allow them to attach non-specifically to a variety
of microorganisms. Once ingested the membrane bound phagosome
containing the microorganism fuses with a lysosome to
form a phagolysosome. The lysosome then releases it contents,
hundreds of degredative enzymes, into the phagolysosome
to destroy the microorganism. The remaining fragments
exit the cell via exocytosis.
However, the legionella bacteria have developed a mechanism
for intracellular growth. The inhibit fusion of the lysosome
and phagosome. Scientists don't know why this happens
but they think the bacteria modifies the membrane using
compounds they secrete or that are present on their surface.
There is little known about the intracellular replication
of legionella. Scientists do know however, that at 4 hours
post-infection, the phagosome is surrounded by a multi
layer membrane derived from the rough endoplasmic reticulum
(RER), and the phagosome acquires an abundant amount of
endoplasmic reticulum-specific protein (BiP). Scientists
don't know the mechanism or significance of this event
and are currently researching the role of the BiP protein
in pathogenicity of legionella.
DAMAGE
The intracellular replication of L. pneumophila within
macrophages is associated with cytopathogenicity, or the
loss of viable cells. However, scientists don't know whether
the cell dies and ruptures because of the strain of the
replicating bacteria, or if the cell undergoes apoptosis,
programmed cell death, to inhibit the bacteria from replicating.
Because macrophages infected with legionella release cytokines
to escalate the immune response, much of the local damage
produced by the infection is attributed to the vigor of
the host inflammatory response.
There is also some debate about the role of bacterial
products. L. pneumophila posses a lipopolysaccharide that
is weakly endotoxic and an extra cellular protease that
has some cytolytic and hemolytic activity. Their is conflicting
evidence on their roles.
Symptoms, Risk Factors, and Diagnosis
SYMPTOMS
Legionnaires' Disease in humans usually begins with flu-like
symptoms: malaise, lethargy, headache, muscle aches and
stiffness, sore joints, and fever.
Virtually all patients next develop the clinical features
of pneumonia: non-productive cough, shortness of breath,
and chest pain.
25-50% of patients experience diarrhea, nausea, vomiting
and abdominal pain.
From the onset of symptoms, a worsening condition is typical
during the first 4-6 days, with improvement starting in
another 4-5 days.
RISK FACTORS
0th. Advanced age
0th. Cigarette smoking
0th. Underlying diseases (cancer, diabetes, renal failure)
0th. Suppressed immune systems (chemotherapy, steroid
medications, diseases)
0th. Alcoholism
0th. Chronic ventilation
DIAGNOSIS
Lab diagnosis is difficult because the bacteria are not
present in large numbers in the sputum, and stain poorly.
Culture is the most specific way to diagnose the infection
although a 3-5 day incubation period is required. In addition,
culture of sputum may be negative in 30-50% of patients
who have legionella infection diagnosed by other ways.
Other signs and tests:
0th. Sputum DFA staining to show legionella
0th. Chest X-ray to show pneumonia
0th. CBC to show increased white blood cell count
0th. PCR
0th. DNA probes
0th. Detection of antigen in the urine
Surprisingly 1/4 of the population has antibodies against
legionella bacteria. 99% of Legionella caused illness
are not severe and are thought to be flu's or mild cases
of pneumonia. There is a 5-15% mortality rate for those
who develop serious cases of Legionnaires' Disease.
Treatment and Prevention
TREATMENT
The goal of treatment is to eliminate the legionella bacterium
with antibiotics. Treatment is started as soon as Legionnaires'
Disease is suspected. Because the bacteria are intracellular,
antibiotics that can penetrate infected cells must be
chosen. Erythromycin is the most widely used, however,
combinations of Erythromycin and Rifampin are often just
as effective.
PREVENTION
The prevention of Legionnaires' Disease is practiced at
an institutional level. In hospitals, hotels, and other
large buildings, water systems are flushed and decontaminated
by hyperchlorination, ultraviolet irradiation, or superheating
of the water. Much of the current research is focused
on ways to prevent Legionnaires' disease outbreaks.
Industrial Water Equipment Ltd
4 Causeway Lane, Matlock
Derbyshire, DE4 3AR
TEL: +44 (0)1629 55839
FAX: +44 (0)1629 501055
2nd Floor, 13 Upper Baggot Street, Dublin
4, Ireland
TEL: + 00 353 14428670
info@industrialwaterequipment.co.uk
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