Serologic observations during an outbreak of rat borne plague in the San Francisco Bay area of California.

Results of a serologic study of a plaque outbreak among rats (Rattus norvegicus) and associated wild rodents are presented. Bacteriologic and serologic evidence points toward mutual exchange of fleas and plaque infection between the intermingled rat and wild rodent populations. Results emphasize the value of serologic methods for epizootiologic studies of plague in North American rat populations.