Leptospirosis disease burden estimation and surveillance networking in India.

Although leptospirosis is known to have occurred in India since the early years of the 20th century, no accurate data on disease burden exist. During the past two decades, leptospirosis cases have been reported with increasing frequency from different parts of the country. Several large outbreaks have occurred. In the year 2000, the Indian Council of Medical Research set up a Task Force on Leptospirosis. The Task Force conducted a multicentric study on disease burden due to leptospirosis. As part of the study, 3,682 patients with acute febrile illness, from 13 different centers in India, were investigated for the presence of current leptospiral infection using the Lepto-dipstick test. Of these patients, 469 (12.7%) were found to have leptospiral infection. The positivity rate ranged from 3.27% in the central zone to 28.16% in the southern zone. Fever, body aches and chills were the common symptoms observed. Urinary abnormalities, such as oliguria, yellow discoloration of urine and hematuria were found in 20%-40% of patients. Distribution of serogroups was studied based on microscopic agglutination test (MAT) titers. The southern zone had all the eleven serogroups in the panel, the eastern zone had nine, the northern zone eight, and the central and western zones had five circulating serogroups each. Among various risk factors studied, rat infestation of houses had the strongest association with leptospiral infection. Many other factors related to the environment, personal and occupational habits, etc, also had significant associations. The study had a few drawbacks. The Task Force has decided to continue the study with modified protocols to generate more accurate and detailed information about disease burden.