Epidemiological trends for human plague in Madagascar during the second half of the 20th century: a survey of 20,900 notified cases

OBJECTIVES To describe the principal characteristics and epidemiological trends for human plague in modern times based on the largest reported series of cases from the highly active Malagasy focus. METHODS We used a file of 20 900 notified cases of suspected plague, 4473 of which were confirmed or probable, to carry out a statistical analysis of incidence and mortality rates and associated factors for 5-year periods from 1957 to 2001. RESULTS Our analysis of trends showed (1) an increase in the incidence rate and the number of districts affected, (2) an increase in the proportion of bubonic forms (64.8-96.8%) at the expense of the pneumonic forms (35.2-3.2%) more frequent in elderly subjects and (3) a decrease in case fatality rate (CFR, 55.7-20.9%) associated with five factors: clinical form, season, province, urban/rural and period considered. The median age of patients was 14 years and more men than women were affected. CONCLUSIONS Since the end of the 1980s, the incidence of plague in Madagascar has increased in both rural and urban areas, because of multiple socioeconomic and environmental factors. However, the plague mortality rate has tended to decrease, together with the frequency of pneumonic forms, because of the strengthening of control measures. Making dipstick tests for the rapid diagnosis of human cases and epizootics in rats available for health structures should make it possible to raise the alarm and to react rapidly, thereby further decreasing morbidity and CFR.