The Philadelphia Legionnaires’ Disease Epidemic of 1976

It wasn’t until this epidemic that a new species of bacteria causing flu-like symptoms and pneumonia was discovered.

René F. Najera, MPH, DrPH


Legionella pneumophila bacteria (via CDC Public Health Image Library)

A quick summary of what you’re about to read, if you don’t have a lot of time:

In 1976, an outbreak of Legionnaires’ disease occurred during the American Legion’s convention in Philadelphia, resulting in 34 deaths and 221 illnesses. The cause was later identified as Legionella pneumophila bacteria in the hotel’s cooling tower, which had spread through the ventilation system. The outbreak led to the identification of the bacteria as the cause of the disease, new regulations for water system maintenance, and increased awareness of the risk of Legionnaires’ disease in public buildings.

Okay, so you do have time… Read on!

In 1976, a mysterious and deadly outbreak of pneumonia occurred in Philadelphia, Pennsylvania. The disease was later identified as Legionnaires’ disease (also known as “legionellosis”), a severe form of pneumonia caused by the bacterium Legionella pneumophila.

The outbreak occurred during the American Legion’s (Pennsylvania Department) 58th annual convention, held at the Bellevue-Stratford Hotel from July 21 to 24, 1976. The convention was attended by over 4,000 members of the American Legion, a veterans’ organization. By the end of the outbreak, 221 people had become ill and 34 had died.

The first person to notice something was wrong was an astute physician who noticed something. As Time magazine put it:

“The first person to see a pattern in the outbreak of illness seems to have been Dr. Ernest Campbell, a physician in Bloomsburg, Pa., who noticed that three patients with the same symptoms had been to a convention together. He called health authorities to arrange for tests but was told that the state laboratory was closed for the weekend.”

As the outbreak continued to spread, a team of epidemiologists from the Centers for Disease Control and Prevention (CDC) was called in to investigate. They collected samples from the hotel’s water system, as well as samples from other…



René F. Najera, MPH, DrPH

DrPH in Epidemiology. Associate/JHBSPH. Adjunct/GMU. Epidemiologist. Father. Husband. (He/Him/His/El)