Changing Patterns of Communicable Disease: Who Is Turning the Kaleidoscope?

CHANGING PATTERNS OF COMMUNICABLE DISEASE: WHO IS TURNING THE KALEIDOSCOPE? DAVID WALTNER-TOEWS* When I was in the midst of my Ph.D. epidemiology program in the early 1980s—a program typically preoccupied with techniques appropriate for the investigation of chronic, non-infectious diseases—I read case reports of a rare condition of immunosuppression in homosexual males. I recall thinking at the time that here was yet another case of pampered North American medical professionals focusing time and energy on a few cases of rare disease in rich Western middle-class people when millions of our fellow humans were dying from tuberculosis, malaria , cholera, and leprosy. I am no longer quite so cavalier, though I confess to remaining sceptical of the notion that whatever is of interest to medical researchers must be of importance to the world. By the late 1980s, when I returned from two years of working in the tropics of Southeast Asia, Lyme disease had risen out of obscurity to become the most commonly reported vector-borne disease in North America [I]. In the early 1990s, the seventh global pandemic of cholera, after a thirty-year wander, finally, inevitably, arrived on the shores of the Americas, and the eighth pandemic, associated with a new, resistant strain of non-01 Vibrio cholera, began its journey along the shores of south Asia [2]. In the southwestern United States, reported cases of plague increased from two to three cases per year in the 1950s to just under 20 per year in the 1980s [3], and an acute viral infection associated with small rodents, previously of interest only to military strategists in East Asia, made its first appearances in North American consciousness [4]. In the first week of October 1994, I received through one of the electronic networks to which I belong a copy of a letter from the Australian Chief Veterinary Officer to the Director General ofthe Office Inter- *Department of Population Medicine, University of Guelph, Guelph, Ontario NlG 2Wl, Canada.© 1995 by The University of Chicago. All rights reserved. 003 1-5982/95/3804-092910 1 .00 Perspectives in Biology and Medicine, 39, 1 ¦ Autumn 1995 43 national des Epizooties in Paris. The letter described an outbreak of acute respiratory disease which resulted in the deaths of 14 horses between September 7 and 26, 1994. Of particular interest and concern was the report that the horse trainer also died of a similar acute respiratory infection on September 27. The causative agent appears to be a virus of the Paramyxoveridae family. Public health officials believe that very close contact with infected horses is required for transmission and that there is no health risk to the general public from this virus. On October 15, an advertisement appeared in The Globe and Mail for a book titled The Hot Zone: A Terrifying True Story, by Richard Preston. "Imagine the scenario," said the ad. "In a Western capital city, a highly contagious, airborne virus that kills 90% of its human victims is raging through a building full of imported lab monkeys . . . But this is no imagined scenario. The virus is Ebola, the city Washington, DC, and these events took placejust five years ago." It is, to me, an alarming sign of the times, of a great vacuum in public consciousness, when people are shocked and surprised to discover that bacteria and viruses are flowing in, around and through us, that close proximity to many different kinds of habitats and animals carries with it risks as well as pleasures, and that those most intimate contacts of all—sex and eating—carry with them, normally, unsurprisingly, and often unavoidably, the highest risks of all [5]· The list of communicable diseases which have caught our attention has, in the last decade, not only solidified the reputations of our old companions—tuberculosis, malaria, salmonellosis, rabies, plague, sexually transmitted diseases—but expanded to include many new names: verotoxigenic E. coli, listeriosis, hantavirus, Ebola, Marburg, Lassa, Kyasunar Forest disease. Anyone staring very closely at the changing patterns of communicable disease could quickly drive themselves crazy trying to make sense of them. Which diseases are the important ones? Which one is the next AIDS, spreading around the globe, and which...