Emergence of plague in the Ikongo district of Madagascar in 1998. 1. Epidemiological aspects in the human population.

Between the 20th October and the 18th November 1990, an outbreak of bubonic plague was declared in a hamlet in the Ikongo district of Madagascar We co nducted an epidemiological survey because of the re-emergence of the diseas e in this area (the last cases had been notified in 1965) and because of th e low altitude compared to the classical Malagasy fod. The outbreak had bee n preceded by an important rat epizootics during September A total of 21 ca ses were registered with an attack rate of 16.7% (21/126) and a letality ra te of 33% (7121). The disease was more prevalent in males (66% of cases) an d children aged <15 years, as observed in general throughout the country. T he anti-F1 seroprevalence among the contact population was 13.5% (13/96), p robably attributable to subclinical infection by Yersinia pestis. No rodent was trapped during the survey but an endemic hedgehog (Tenrec ecaudatus) w as highly seropositive, suggesting a recent transmission of the plague baci llus among this species, The small mammals and vectors possibly involved in these new foci were investigated in May 1999.