More than 90% of Legionella cases are
caused by Legionella pneumophila, a bacterium
that thrives in warm to hot water. Pipes,
tanks, faucets, showerheads, and hot water
heaters are ideal breeding grounds for L.
pneumophila. Since infection with Legionella
occurs through inhaling the bacterium, any
activity in which contaminated water can
be misted and subsequently inhaled can lead
to infection. Cooling towers, such as those
used in large systems, as well as evaporative
coolers, hot water systems, showers, whirlpool
spas, decorative fountains, hot tubs, ice-making
machines and room air humidifiers are all
potential sources of Legionella. Cruise
ships, hotels, hospitals, nursing homes
and office buildings are particularly susceptible.
Outbreaks of Legionnaires’ Disease usually
occur in the summer and early fall. The
overall fatality rate from Legionella is
from 5% to 30%. However, the death rate
among patients who contract the disease
while they are already in the hospital for
something else is close to 50% (http://www.nlm.nih.gov/medlineplus/ency/article/000616.htm),
which corroborates the observation that
most infections occur among the middle-aged
or older, smokers, people on immunosuppressive
therapy or corticosteroids, those who have
had recent organ transplants and those with
chronic pulmonary problems are also at elevated
risk. People who have weakened immune systems
from cancer, cancer treatments, diabetes
and kidney failure are also more susceptible
to infection with Legionella.
The first recognized outbreak of Legionnaires’
Disease occurred on July 27, 1976 during
an American Legion convention in the Bellevue
Stratford Hotel in Philadelphia, PA. Two
hundred and twenty one (221) people were
sickened with pneumonia, and 34 died. The
U.S. Centers for Disease Control (CDC) finally
isolated the causative agent: a previously
unknown bacterium called Legionella pneumophila.
The organism was found concentrated in the
hotel’s A/C cooling tower, from which it
was able to spread throughout the hotel.
(http://en.wikipedia.org/wiki/Legionellosis).
It is difficult to diagnose Legionnaires’
Disease on the basis of symptoms or X-ray
findings because its just like other forms
of pneumonia. Once we began looking for
evidence of Legionella infections, especially
with the urinary antibody test, we discovered
that between 10,000 and 50,000 cases occur
in the U.S. each year, and between 8,000
and 18,000 are sick enough to be hospitalized.
The Occupational Safety & Health Administration
(OSHA) estimates that Legionellosis causes
more than 25,000 cases and 4,000 fatalities
each year (http://www.osha.gov/SLTC/legionnairesdisease/index.html).
Nonetheless, the Centers for Disease Control,
CDC, estimates that many more cases are
either not diagnosed or not reported (http://www.cdc.gov/legionella/patient_acts.htm).
Facts About Legionnaires’
Disease (Legionella pneumophila)
As many as 40% to 60% of tested cooling
towers contained Legionella (CTI Legionellosis
Guideline: Best Practices for Control of
Legionella (WTP-148) (06)). It is reasonable
to assume a similar rate in other engineered
water systems as well. Water mists containing
viable Legionella organisms can travel as
far as 10 kilometers (6.2 miles). The European
Working Group for Legionella Infections
(EWGLI) has published guidelines for recommended
actions to take when water system test results
show levels of Legionella (EWGLI: Technical
Guidelines for Control of Legionella in
Water Systems). According to EWGLI, if a
tested water supply system shows 1,000 Colony-Forming
Units per milliLiter of water (CFU/mL),
the system is considered to be under control.
If the test shows more than 1,000 CFU/mL,
up to 10,000, EWGLI recommends immediate
verification by re-testing. If confirmed,
do a risk assessment and identify remedial
actions to be taken. Above 10,000 CFU/mL,
EWGLI recommends immediate re-testing followed
by “shocking” the system with biocide, and
implementing remedial actions for longer-term
effect.
Some localities require regular Legionella
testing in certain types of buildings. The
decision to test or not to test must be
made on a case-by-case basis, taking into
consideration such factors as potential
for inhalation exposure, the age and general
health status of those who might be exposed
and the nature of the water system.
The professionals at Atlantic Environmental
are well-versed and experienced in sampling
for Legionella pneumophila. We can assist
you in setting up a risk assessment and
sampling program to help you stay in control
of your water system. Call us at 800-344-4414
or e-mail at info@atlenv.com.
