More heroic sagas of the now-celebrated Centers for Disease Control. Magazine writer Astor is inclined to overreport names, numbers, and dates, but essentially these are good yarns, smoothly and competently told. A scene-setting chapter describes the CDC and its Epidemiology Program Office--where investigators can sign up for two-year hitches (which satisfy military obligations). These bright-eyed, bushy-tailed young men and women are the heroes of the narratives that follow. They include cases of salmonella linked to contaminated marijuana and cholera traced to cooked crab (the vibrios occasionally multiply in food and may have been protected from heat by sequestering near the hard shell). There are full accounts, too, of Legionnaire's disease, toxic shock syndrome, hemorrhagic fevers, odd outbreaks of bubonic plague, and other horrors, as well as the latest on the ""Gay Men's Disease"" (AIDS)--with the poignant note that, for some dying victims, revelation of the disease meant disclosure of their homosexuality to wives and family. Astor also discusses CDC's inconclusive explorations of associations between exposure to Nevada nuclear-testing sites and later cases of leukemia or other serious disease. A final chapter puts epidemic disease in perspective with some considerations of the endless battles between infectious agents and susceptible populations: old organisms that mutate, or grow resistant; new organisms or mysterious ailments that baffle doctors (like the strange deaths-in-sleep documented among Hmong refugee-tribesmen from Vietnam). Environmental hazards and lifestyle-habits can also be causes of morbidity, Astor notes, stressing the importance of CDC in recording the risks and establishing means of prevention. A little politics, then, but chiefly medical drama.