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Yesterday I wrote about a recent outbreak of Legionnaire’s Disease
in guests staying at the Plim Plaza Hotel in Ocean City, Maryland.

As a
Legionnaire’s Disease attorney, I want to use today’s blog to talk more about what Legionnaire’s
Disease is, and how people get it.

The Origins of Legionnaire’s Disease as a Named Illness

Legionella existed long before it had a name. But with the advent of air
conditioning and hot tubs, people created environments that enabled the
bacteria to breed and become airborne.

Legionella pneumophila, the type of bacteria that cause Legionnaire’s
disease, is found naturally in water such as lakes and rivers. In nature,
however, legionella is rarely dangerous, because it is so diluted.

The illness caused by legionella is called Legionellosis, and it comes
in two forms: Legionnaire’s disease is the more serious form and
involves pneumonia; the milder version is called Pontiac Fever.

Scientists actually discovered the milder form – Pontiac Fever –
first. Pontiac Fever was first recognized after a major outbreak in Pontiac,
Michigan, in 1968. 95 of 100 employees of the Oakland County Health Department,
and 49 of 170 visitors to the Department, became sick. CDC sent three
investigators into the building, and they, too, became sick. CDC dispatched
three more investigators, and these three also became sick. Investigators
finally discovered that the outbreak was stemming from an evaporative
condenser in the basement. This condenser was vented to the roof, and
the vent emerged just two meters from an air intake unit – meaning
the legionella was being pulled back into the building. See Legionnaire’s
Disease Pathogenicity and Design Considerations, Penn State’s Department
of Architectural Engineering, at

Then, in 1976, a group of people attending the American Legion Convention
in Philadelphia came down with a mysterious illness. When several people
died, investigators were brought in. Medical experts traced the outbreak
to bacteria found in the air conditioning unit at the hotel where the
conventioneers had stayed. The disease was called Legionnaire’s
Victims because it had affected Legionnaires attending the convention.


Who Are the Victims of Legionnaire’s Disease?

Because Legionnaire’s disease strikes the lungs, it disproportionately
affects smokers and people with chronic lung disease. It also is more
common and more dangerous for people with weakened immune systems (premature
infants, transplant recipients, AIDS sufferers, hospital inpatients, etc.).
Outbreaks of Legionnaire’s disease in hospitals are extremely dangerous
because hospitals are filled with the people most vulnerable to the disease.

How Many People Get Legionnaire’s Disease?

CDC estimates that “8,000 to 18,000 people get Legionnaire’s
disease in the United States each year.” A sobering 30% of those
people die, according to CDC statistics. Id. Generally Legionnaire’s
disease has an incubation period of two to fourteen days; Pontiac Fever
cases may have a shorter incubation period. Id.

While large outbreaks do receive media attention, experts believe that:
“this disease usually occurs as a single, isolated case not associated
with any recognized outbreak.” See, e.g.,,
disease_and_pontiac_fever/article.htm. In fact, many experts believe that
the incidence of Legionnaire’s disease is much higher than reported,
because many cases either are not identified as the Legionnaire’s
disease form of pneumonia, or are never associated with a particular outbreak.

How Does Legionella Breed?

Legionella becomes dangerous when it is allowed to breed in the warm, stagnant
water of cooling towers and whirlpools. People become infected when they
breathe in the mist that contains the legionella bacteria. Outbreaks have
happened in office buildings, hotels and hospitals, and around pools and
whirlpools in hotels and cruise ships. A recent outbreak was believed
to be the result of water droplets spraying from an air conditioner unit
on the top of a building. The spray reached the sidewalk area below, infecting

Legionella can breed when air conditioners, pools, or whirlpools are not
properly cleaned. It also can be distributed through poorly designed buildings
or cooling systems that direct contaminated water droplets directly into
the air that people breathe. On the other hand, Legionnaire’s disease
is almost always preventable with good maintenance and building design.

The author of this blog,
Legionnaire’s Disease attorney Lee Wallace represented six people who contracted Legionnaire’s
Disease and Pontiac Fever in a 2001 outbreak at a Georgia hotel. In that
case, a hotel had failed to clean its hot tub spa, and had not bothered
to use enough chemicals to keep the bacteria at bay.