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"Hello, I'm part of the medical team investigating this weird disease," said Dr. Stephen Thacker, 28, as he sat down beside Thomas Payne's bed in Chambersburg Hospital. "How do you feel? When did you first feel sick? Where did you eat and stay in Philadelphia? When did you arrive there? When did you leave? Did you go to the testimonial dinner? Or the go-getter's breakfast? Did you go to the hospitality rooms for the state commander or other officials? Did you have any contact with pigs?"
In some ways the detectives' legwork raised more questions than it answered. A check of the hotels at which the conventiongoers had stayed revealed no outbreak of the mysterious illness among employees who had come in contact with the Legionnaires. The investigators could find no evidence that any of the victims had been exposed to pigs, which have been implicated as the animal reservoir for the swine-flu virus. Nor could the disease detectives explain another apparent contradiction: why some people developed the disease, while others, who ate the same meals, drank the same drinks or shared their rooms during the convention, did not. "This is an amazing disease," said Dr. Robert Gens, director of Pennsylvania's bureau for adult health services. "People dying quickly of interstitial pneumonia is really amazing."
The failure of the interviewers to find the answer put the main burden on the scientific sleuths working in state and federal laboratories. Their task involved a painstaking process of elimination, in which known disease agents were sought, and, if absent, exonerated.
One of the first suspects to be screened—because potentially most worrisome on a national scale—was swine flu, a seemingly virulent form of influenza that first surfaced last winter at Fort Dix, N.J., where it infected about a dozen soldiers and killed one. Swine flu may also be related to the flu that killed over half a million Americans in 1918-19 (see box). Some felt that the rapid onset of the Legionnaires' disease was typical of flu. Others thought that the appearance of a condition similar to viral pneumonia, which can also be a result of influenza, was a convincing clue.
To determine if influenza was the killer, the researchers took solutions made from tissues taken from disease victims and injected them into three kinds of cultures—chick embryos, human and monkey cells, and live mice. The viruses would indicate their presence by killing the living cells and by killing or infecting the mice. They would reveal their existence in the chicks indirectly. Fluid from the infected chick eggs was mixed with samples of normal animal blood to see if the embryonic cells would agglutinate, or "clump" together; if they did, it would mean that a virus was present.
Some doctors hoped, in a way, that the tests would show that the villain was indeed an influenza virus, since at least some vaccines against flu were already available for use. But it was not to be so simple a case. After reviewing the results of their first set of tests, scientists ruled out swine flu or any flu as a suspect.