Soon after Philadelphia hosted America’s bicentennial celebrations in late July 1976, more than 200 attendees of the American Legion Convention at the Bellevue-Stratford Hotel in Philadelphia fell ill with pneumonia symptoms, including fever, cough and trouble breathing.

Thirty-four of them died.

One of us was a newly minted pulmonary fellow at Hahnemann University Hospital. The hospital was just a mile from the hotel and received some of the first cases.

At the time, no one knew what caused the illnesses. Scientists considered bacterial or viral infection, heavy metal toxins or some combination of environmental causes.

Early days of Legionella pneumophila

Several months later, Dr. Joseph McDade, a microbiologist at the Centers for Disease Control and Prevention, discovered the organism that was responsible after doing detailed microbiological investigation and animal testing.

The newly recognized bacteria was named Legionella pneumophila after the outbreak at the Legionnaires’ convention.

Legionella pneumophila differed from infectious respiratory organisms known at the time since it multiplied in an environmental water source and was not spread by person-to-person contact.

It was also atypical because these bacteria do not have cell walls and appear colorless with the usual laboratory staining methods – making them difficult to identify.

The CDC found that........

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