Outbreak Surveillance Report on Pulmonary Leptospirosis after a Heavy Floods during 2006 in South Gujarat

Background: During the heavy rainfall season in the Surat district of South Gujarat India, from July to October 2006 an outbreak of leptospirosis occurred. Aim: This article reports the exposure of leptospirosis in this post flood outbreak. In total 1,258 patients of New Civil Hospital in Surat were included, based on their clinical signs and symptoms for leptospirosis. Severe pulmonary hemorrhages were observed in the imperative form in most cases encountered during this season. Method: Laboratory investigation was carried out using rapid diagnostic tests like Leptocheck WB, Serion IgM ELISA and real-time PCR and they were evaluated for the outbreak investigation in comparison with the microscopic agglutination test (MAT) Observation and Results: The predominant serovars encountered by the gold standard MAT were autumnalis(46%), australis(38%), pyrogenes(30%), cynopteri(20%), icterohemorrhage(8%) and grippotyphosa(1.6%). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of rapid tests were analyzed, Leptocheck WB (91%, 78.4%, 83% & 88.3%), Serion IgM ELISA (92.2%, 89.4%, 90.3% & 91.6%) and Real time PCR (90.3%, 91.6%, 96.02% & 96.02%) using statistica (6.0). The incidence of the disease was greater during the month of August (41.41%) and September (52.94%) with a relative risk of 33.5 in Surat. Conclusion: This implicates the impact of the heavy rainfall and flood as the cause for severe outbreak of leptospirosis among the urban population of Surat district. Frequently contaminated environmental exposures due to urbanization and industrialization were speculated as major cause for this severe epidemic during heavy floods, which entails preventive strategies and prompt treatment against leptospirosis under such outbreak circumstances.