Plague in Brazil during two years of bacteriological and serological surveillance.

In north-east Brazil, where plague infection is endemic, bacteriological and serological methods were employed during a two-year period to determine accurately the occurrence of human infection and to define certain epidemiological features of both human and rodent infection. There were 67 confirmed cases of plague, predominantly among males and children. Most of these cases occurred in two inland rural plateaux of Ceara State. Clustering of cases in place and time was common, as was a history of contact with rats. Peak occurrence was in November 1978, during the warm, harvest time of year. Rodent surveillance resulted in isolation of Yersinia pestis from 33 animals, most of them from the field rodent, Zygodontomys pixuna, in the States of Pernambuco and Ceara. Our results indicate a decline in the number of human cases from previous years but show that several foci remain active and that serological testing, in addition to routine bacteriological testing, can assist workers in maintaining the surveillance of both human and rodent plague in Brazil.