Found: The Philly Killer, Perhaps

Despite its past triumphs, the U.S.

Public Health Service's Center for Disease Control has had a bad press lately. As the Government's front-line fighters against epidemic disease, the CDC's dedicated scientists had to take much of the blame, justly or not, for the collapse of the nationwide swine flu program. Equally embarrassing, they were unable to identify the mysterious fever that killed 29 people and hospitalized scores of others after an American Legion convention in Philadelphia last summer.

Last week, after months of patient investigation, CDC officials in Atlanta proudly announced that one of the agency's researchers had apparently found the cause of Legionnaires' disease. The likely culprit: a hitherto unknown rod-shaped bacterium that also may have caused an unexplained outbreak of a pneumonia-like disease that killed at least 16 people in 1965 at St. Elizabeths Hospital in Washington, D.C.

The discovery was made not by a man who hunts ordinary bacteria, but by a microbiologist who specializes in leprosy and rickettsial diseases like typhus and spotted fever. The latter are characterized by fever, headaches and general malaise and are caused by bacteria-like microorganisms usually carried by ticks, lice and fleas. But when Dr. Joseph McDade, 36, examined the lung tissue of victims of last summer's outbreak, he found no trace of any rickettsiae.

Refusing to give up, McDade decided during the Christmas holidays on a new approach: to look for a strange organism rather than a familiar one. It was difficult, tedious work, he recalls, "like searching for a missing contact lens on a basketball court with your eyes four inches away from the floor."

Telltale Symptoms. As a first step, he inoculated his guinea pigs with lung tissue from two victims of Legionnaires' disease. Within a day or so, the lab animals developed telltale symptoms: fever, lethargy, watery eyes. Then McDade injected material from their spleens into chick embryos, which also became infected, and died within six days.

Finally, while examining the yolk sacs under a microscope, he found a cluster of bacilli different from any he had seen before. When he mixed these with blood from survivors of Legionnaires' disease, he found antibodies against them in 29 out of 33 specimens, which indicated that the people had prior exposure to the bacterial strain. Tests on blood from victims of the St. Elizabeths infection--which had been carefully preserved in Atlanta in hopes of some day solving that puzzle--showed identical antibodies.

McDade points out that there is still a small chance that the new bacterium may turn out to be a secondary invader rather than the disease agent itself. But for the moment, the disease sleuths think they have their bug and are now trying to fit the bacterium--which as yet does not even have a nickname--into its proper niche in the microbial world. They are also trying to answer major questions about it: How and where does it grow? How is it transmitted? (Legionnaires' disease is apparently not carried from one person to another.) One reassuring fact has already emerged. The mysterious bug is what McDade calls a "fastidious bacterium": not only hard to grow, but also extremely choosy about where it lives. That should help reduce the risk of any recurrences of last summer's tragic epidemic in Philadelphia.

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