Hunting for the Hidden Killers: AIDS

Disease detectives face a never ending quest

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With a malady of unknown cause, the first step is to decide how to define it. "We wanted the definition to be broad enough to include most cases, but not so broad that it would include everybody with a cold," Tsai recalls. Six EIS agents fanned out across the state, questioning other suspected victims. Where did they eat and drink? Were the windows open in their hotel rooms? What events did they attend? A more detailed survey went out to all 4,400 Legionnaires who had attended the convention, and 3,500 were returned within three days. Other agents followed up stray leads, like a call from a magician who admitted lighting a sparkler at the hotel. Back in Atlanta, clinicians noticed the high white blood cell counts in specimens from the victims, and began to search for bacteria under their microscopes.

At first CDC experts suspected an attack of swine flu, which health officials had been fearing that year. But the evidence did not support that hypothesis. Some who had merely walked past the hotel contracted the disease. Yet it was noncontagious: no one caught it from the original 182 victims, 29 of whom died. Nor were any bacteria found. "The picture slowly evolved that we didn't know what we were dealing with," Tsai remembers.

The outbreak vanished as quickly as it began, but researchers at CDC, including Microbiologist Joseph McCade, 43, continued to examine the specimens taken from the victims. Five months after the convention, he took another look at some red sausage-shaped bacteria and concluded that they were the culprits. They had festered in the water of the hotel's cooling tower and had been carried through the air as the water evaporated. The antibiotic Erythromycin proved effective in treating the disease, and many similar cooling towers across the country are now chlorinated to guard against another outbreak.

Another famed mystery was solved primarily by the epidemiologists rather than the lab scientists. In January 1980, doctors in Wisconsin and Minnesota noticed that an unusual number of young women were suddenly developing high temperatures and low blood pressure, with potentially fatal results; out of the 55 patients in the CDC's initial study, seven had died by the end of May. Dr. Kathryn Shands of EIS led the CDC investigation, developing a clear definition for what soon became known as toxic shock syndrome and recording in detail all the cases.

A staphylococcus bacterium was clearly the cause of the outbreak, but the medical question was "Why?" Through further epidemiological studies, the medical sleuths found that most of the new cases under investigation involved menstruating women who had been using tampons. A majority had used Procter & Gamble's Rely tampons, a new superabsorbent brand, which may have provided an environment that encouraged bacterial growth. After the product was removed from the market, the number of reported toxic shock cases dropped sharply.

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