Epidemiological and diagnostic aspects of the outbreak of pneumonic plague in Madagascar

Background Plague is a re-emerging disease and pneumonic plague is the most feared clinical form. We describe a well-documented outbreak of pneumonic plague in Madagascar. Methods Field epidemiological data were collected. Biological tests (microscopy, culture of Yersinia pestis, F1 antigen ELISA and dipstick assays, IgG anti-F1 ELISA) were done on sputum, serum, or necropsy samples. The infection rate among 154 contacts was assessed by anti-F1 serological techniques. Findings The index case was a bubonic patient with a secondary lung infection, who contaminated a traditional healer and his family. Funeral ceremonies and attendance on patients contaminated other villagers. In total 18 cases were recorded, and eight died. F1 antigen could be detected in sputum by ELISA and dipstick tests as early as the second day after the onset of the symptoms and also 48 h after treatment. Among the contact population 13 of 154 (8•4%) have been exposed to the plague bacillus (symptomless or latent infections). Interpretation The F1 dipstick assay on sputum is an invaluable diagnostic tool for pneumonic plague. Treatment of patients and chemoprophylaxis of contacts were efficient in stopping the epidemic.