Emerging viral infections

R. T. Johnson
Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Md., USA.

New microbial threats to human health and survival have arisen intermittently over the centuries. The increasing global population provides greater numbers of hosts for mutational evolution and sufficient hosts to ensure maintenance of new agents; the magnitude and modes of modern travel make a larger population of susceptible people accessible and provide rapid spread of infectious agents. This milieu is particularly hospitable for viruses; therefore, in the future we can anticipate increasing numbers of emerging viral diseases. This article on microbial threats has been limited to viruses associated with neurological diseases.