Evidence that at least two biologically distinct viruses are involved in the disease currently diagnosed as swine pox is reported by Shope1 of the Rockefeller Institute in Princeton, N. J. For at least sixty years the relation between the various pocklike conditions of man and domestic animals has been controversial. The majority opinion about twenty years ago was summarized by Gins2 of the Robert Koch Institute, Berlin. He found that human smallpox could be adapted to cows, sheep, goats and swine by "lapinization" (serial passage in rabbits), from which he concluded that all pocklike diseases are of common microbic origin. A few veterinarians3 of that time disputed this opinion. They reported, for example, absence of cross immunity between natural swine pox infection and experimental inoculation with vaccinia virus.
Swine pox, prevalent in the United States, is encountered with particular frequency in the Middle Western states. The disease
SWINE POX AND VACCINIA. JAMA. 1941;117(19):1627. doi:10.1001/jama.1941.02820450051016