Evolving epidemiology of Nipah virus infection in Bangladesh: evidence from outbreaks during 2010-2011

Abstract

Drinking raw date palm sap is the primary route of Nipah virus (NiV) transmission from bats to people in Bangladesh; subsequent person-to-person transmission is common. During December 2010 to March 2011, we investigated NiV epidemiology by interviewing cases using structured questionnaires, in-depth interviews, and group discussions to collect clinical and exposure histories. We conducted a case-control study to identify risk factors for transmission. We identified 43 cases; 23 were laboratory-confirmed and 20 probable. Thirty-eight (88%) cases died. Drinking raw date palm sap and contact with an infected person were major risk factors; one healthcare worker was infected and for another case transmission apparently occurred through contact with a corpse. In absence of these risk factors, apparent routes of transmission included drinking fermented date palm sap. For the first time, a case was detected in eastern Bangladesh. Identification of new epidemiological characteristics emphasizes the importance of continued NiV surveillance and case investigation.

Keywords: Encephalitis; Nipah virus; nosocomial infection; outbreak.

Fig. 1

Geographical location of Nipah encephalitis cases identified during the 2010–2011 Nipah season in Bangladesh.

Fig. 2

Distribution of date of onset of illness of Nipah encephalitis cases identified during the 2010–2011 Nipah season in Bangladesh.