Transmission of Epidemic Influenza

THE PLAGUE YEARS Mankind has always been fascinated by "origins," and biologists are no exception. Darwin is our most famous example. What is the origin of mankind, of species, of infectious diseases? In the last few years we have seen the emergence and spread of some apparently "new" viruses, such as HIV -1 and the virus causing bovine spongiform encephalomyelopathy. But are these, in fact, entir...