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Legionnaires' disease: cause, diagnosis and treatment

Yale Rosen
Legionella bacteria

Legionnaires' disease has been in the news recently with cases in New York City and Syracuse. But many people don’t know much about the illness other than it derives its name from a 1976 Legionnaires’ convention when attendees contracted the disease.

The good news is that much has been learned about the Legionnaires’ since then. Much of that knowledge is due to the work of Janet Stout, one of the top authorities on Legionnaires' and an engineering professor at the University of Pittsburgh.

In 1976, 221 attendees at the Legionnaires’ convention in a Philadelphia hotel contracted the disease, and 34 of them died.

Legionnaires’ disease is a kind of pneumonia spread through the legionella bacteria. Unlike other some other kinds of bacteria that sickens humans, this one is spread through water, not by person-to-person contact. The bacteria usually live in manmade water systems, like in buildings.

People contract the disease by breathing in mist with the bacteria or they drink the water, but it has to get into the lungs, says Stout.

But it can be difficult to figure out where Legionnaires’ is coming from, says Stout. For one reason, the time of exposure to legionella bacteria to a patient showing signs of Legionnaires’, like fever and cough, can be anywhere from two to 10 days.

First a person will be diagnosed with pneumonia, before being diagnosed with Legionnaires’. Special diagnostic tests most be ordered to identify that the source is Legionnaires’.

Usually the people who actually contract the disease are the people who are risk factors that increase their probability to get it – smokers, diabetics, people with lung disease are those who are immune-compromised, says Stout.

There are antibiotics that are quite effective in treating Legionnaires’. Stout says the problem arises when it patients take too long to get medical attention or it’s not diagnosed quickly enough.