Risk factors for Nipah virus encephalitis in Bangladesh

Abstract

Nipah virus (NiV) is a paramyxovirus that causes severe encephalitis in humans. During January 2004, twelve patients with NiV encephalitis (NiVE) were identified in west-central Bangladesh. A case-control study was conducted to identify factors associated with NiV infection. NiVE patients from the outbreak were enrolled in a matched case-control study. Exact odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by using a matched analysis. Climbing trees (83% of cases vs. 51% of controls, OR 8.2, 95% CI 1.25-infinity) and contact with another NiVE patient (67% of cases vs. 9% of controls, OR 21.4, 95% CI 2.78-966.1) were associated with infection. We did not identify an increased risk for NiV infection among persons who had contact with a potential intermediate host. Although we cannot rule out person-to-person transmission, case-patients were likely infected from contact with fruit bats or their secretions.

Figure 1

Top: Distribution of Nipah virus case (n = 12) and control (n = 36) households within the outbreak/study site of Goalando township, Bangladesh, January 2004. Number in the yellow triangle corresponds to household no. in Figure 2. Map also shows extreme habitat disturbance; areas under cultivation (for rice, sugar cane) are highlighted with “C,” and remaining trees (fruit trees and bamboo stands) with “T.” Bottom: Location of outbreak village.

Figure 2

Epidemic curve of Nipah virus outbreak in Goalando, Bangladesh, in 2004, demonstrating household clustering. Households 1 and 4 each had 2 cases, household 5 had 3 cases, and all other households, single cases.