Experimental smallpox in chimpanzees.

In an attempt to prepare highly specific antiserum to variola virus, a chimpanzee was inoculated with a virulent human strain of this virus. Three uninoculated chimpanzees were housed in the same room; two of these developed clinical disease with seroconversion, while the third developed no evidence of infection and no antibody. The three animals that became ill also developed antibody to vaccinia and monkeypox viruses. Human contacts during the study and following a break in containment showed no evidence of infection as determined by serological tests and lack of clinical disease.