Saturday, July 17, 2010

Legionnaire's Disease

Medical Meanderings 14 October 2009

Philly Mystery (c)

“In solving a problem of this sort, the grand thing is to be able to reason backwards…but people do not practice it much.”
- Sherlock Holmes, in “A Study in Scarlet” (Sir Arthur Conan Doyle)

In July 1976, the Pennsylvania chapter of the American Legion, a non-political organization of military veterans, met in Philadelphia. Ten thousand men attended, but within days of returning from their convention, a dozen attendees were dead, and several others were hospitalized, due to a mysterious respiratory illness. Those affected were suffering with a rapidly-progressive pneumonia and fevers exceeding 107 degrees Fahrenheit.

The summer of 1976 was not very different from the summer of 2009. The country was primed with a fear of an infectious epidemic. The Ford administration was preparing to vaccinate the public against an unusual, spreading strain of influenza called “swine flu.” The media fed the fear, with Michael Crichton’s novel “The Andromeda Strain,” about the terrifying spread of a devastating pathogen, becoming a best seller. Then the news broke in early August about the new, fatal “Legion disease” in Pennsylvania, the cause of which had not been found.

Pennsylvania state health workers had initially responded to the epidemic by preparing for a medical disaster while reassuring the public that the crisis was under control. Help was soon requested, and the Communicable Disease Center (now the Centers for Disease Control and Prevention, or CDC) sent twenty federal disease investigators to assist dozens of state investigators. The CDC’s investigators were members of the Epidemiology Intelligence Service, the federal government’s “rapid response team” of physicians and public health scientists sent to do the detective work in any potential epidemic.

By the end of the epidemic, the disease had infected 221 Legionnaires and killed thirty-four. The medical investigators had spread across Pennsylvania, reviewing hospital records, attending autopsies and investigating the sites involved in the July convention. Initially, influenza was suspected, but none of the victims tested positive for the influenza virus. The investigators followed several other false leads, including the possibility that the Legionnaires had been exposed to a toxin, heavy metal or poison.

It took six months to identify the culprit of this epidemic, a newly-discovered bacterium that was named (in honor of this outbreak) Legionella pneumophilia (meaning “preferring the lungs”). Legionella prefers to live and grow in standing water. It had contaminated the plumbing within the convention hotel, then infected its victims through shower heads and faucets.

Legionnaire’s disease, as it is now known, is still relatively common, causing up to 10% of severe pneumonia with high fevers. Frighteningly, it has been found in up to 70% of hospital water systems in some geographic regions! However, we have diagnostic tests and antibiotics available to diagnose and treat Legionnaire’s disease that were not available in 1976. Nevertheless, there are lessons to be learned in the story of Legionnaire’s disease. The confusion and chaos of media-driven public fear can hinder progress and lead to irrational panic. On the other hand, the effectiveness of medical detective work and the scientific method is clear.

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