Unless they're eradicated smallpox-style, infectious diseases never disappear. Like an unlucky penny, they can show up at any time.
The reason is because most microbes can survive elsewhere, either in the environment or other animals or both, a concept known as a "reservoir." That is why prevention is the key to public health. And prevention is achieved primarily through practices such as vaccination, water chlorination, pasteurization, sanitation, and good personal hygiene (as well as common sense). If we take away any one of these practices, we can expect relatively rare infectious diseases to come back. Three stories serve to underscore this crucial lesson.
Rabies in Seattle
Recently, a bat was lying on the ground on the University of Washington...