The Epidemiology of the Origin and Perpetuation of a New Disease

PERSPECTIVES IN BIOLOGY AND MEDICINE Volume VII · Number 3 · Spring 1964 THE EPIDEMIOLOGY OF THE ORIGIN AND PERPETUATION OF A NEW DISEASE RICHARD E. SHOPE* I. The Origin It is peculiarly appropriate that a Ricketts Lecture should deal with matters pertaining to the origin and perpetuation ofan infectious disease because the work for which Howard Taylor Ricketts is best known concerned these very matters. Rocky Mountain Spotted Fever, when Ricketts began his investigations ofit, was a mysterious, frequently fatal, typhuslike ailment occurring each spring and early summer in parts ofthe western United States. No one knew from whence it came each year, what its cause was, why it was seasonal, or where it disappeared to. Ricketts, by scientific sleuthing, requiring much imagination, originality, and scientific skill, solved the entire mysteryoftheorigin andperpetuationofthe disease. The story, after itwas completely unraveled and worked out, seemed perfectly simple, as do many great scientific discoveries after they are finally made. Even today, however, over fifty years after his pioneering work, one can only marvel at the skillful and ingenious manner in which he discovered the causative agent of spotted fever, learned the secrets of its method ofperpetuation through a cycle involving ticks and small rodents, and explained its cyclical reappearance each year. He later worked with typhus fever and found in this disease an agent similar to the one hehad shown inspotted fever. Itwas during these studies that he acquired the laboratory infection ofwhich he died on May 3, 1910. His contributions to our knowledge of that group of infectious diseases caused by organisms ofthe type that resulted in his death were numerous * Member and Professor, The Rockefeller Institute, New York. This Howard Taylor Ricketts Lecture was presented May 31, 1963, at the University ofChicago Medical School. 263 and important. Fellow scientists, recognizing the great role Ricketts had played in the discovery ofthese pathogens, perpetuated his name by calling the genus Rickettsia in his honor. Dr. Ricketts, though his scientific career was short, made it a brilliant one by the magnitude ofhis discoveries. The story that I have to tell about the epidemiology ofthe origin and perpetuation of a new disease has some things in common with spotted fever, but in other respects it is quite different. For instance, while man is involved in both, in spotted fever he was the victim; in my story he is the villain. The causative agent in my disease is a virus rather than a rickettsia. However, it does have a reservoir host, though this is quite diffèrent from the ticks which Ricketts found perpetuated spotted fever. My disease has a seasonal incidence,just as has spotted fever, but for quite a diffèrent reason . There are other points of similarity and dissimilarity, but they will emerge as I tell the story. The disease I am talking about is swine influenza, which appeared for the first time in the late summer or early autumn of1918. So far as anyone who observed the original outbreak could tell, a disease ofswine like this one had never before been seen, and there was general agreement among veterinarians and farmers that it was a completely new one. The exact date or locality ofits initial occurrence remains unknown, but careful observers have stated that cases were seen as early as August on farms in western Illinois. It is certain that the disease caused serious losses among swine on exhibition at The National Swine Breeders Show held in Cedar Rapids, Iowa, from September 30 to October 5. At the conclusion of the show, the swine, many ofthem ill, were returned to their home farms, and within two or three days this new disease was stated to be rampant in the portion ofthe drove thathadremained athome. Shortly thereafter it became widespread among swine herds in Iowa and other parts of the Middle West. This first outbreak of swine influenza was no small or minor affair, for during the three or four months at the end of 1918 when it prevailed, literally millions ofswine became ill and thousands died ofit. The disease has recurred each year since 1918. These recurring annual outbreaks have begun in the late autumn and persisted for about three months before abating...