Isolation and Full-Genome Characterization of Nipah Viruses from Bats, Bangladesh.

Despite molecular and serologic evidence of Nipah virus in bats from various locations, attempts to isolate live virus have been largely unsuccessful. We report isolation and full-genome characterization of 10 Nipah virus isolates from Pteropus medius bats sampled in Bangladesh during 2013 and 2014.

Convergence of Humans, Bats, Trees, and Culture in Nipah Virus Transmission, Bangladesh.

Preventing emergence of new zoonotic viruses depends on understanding determinants for human risk. Nipah virus (NiV) is a lethal zoonotic pathogen that has spilled over from bats into human populations, with limited person-to-person transmission. We examined ecologic and human behavioral drivers of geographic variation for risk of NiV infection in Bangladesh. We visited 60 villages during 2011-2013 where cases of infection with NiV were identified and 147 control villages. We compared case villages with control villages for most likely drivers for risk of infection, including number of bats, persons, and date palm sap trees, and human date palm sap consumption behavior. Case villages were similar to control villages in many ways, including number of bats, persons, and date palm sap trees, but had a higher proportion of households in which someone drank sap. Reducing human consumption of sap could reduce virus transmission and risk for emergence of a more highly transmissible NiV strain.

Seroepidemiological Study of Interepidemic Rift Valley Fever Virus Infection Among Persons with Intense Ruminant Exposure in Madagascar and Kenya.

In this cross-sectional seroepidemiological study we sought to examine the evidence for circulation of Rift Valley fever virus (RVFV) among herders in Madagascar and Kenya. From July 2010 to June 2012, we enrolled 459 herders and 98 controls (without ruminant exposures) and studied their sera (immunoglobulin G [IgG] and IgM through enzyme-linked immunosorbent assay [ELISA] and plaque reduction neutralization test [PRNT] assays) for evidence of previous RVFV infection. Overall, 59 (12.9%) of 459 herders and 7 (7.1%) of the 98 controls were positive by the IgG ELISA assay. Of the 59 ELISA-positive herders, 23 (38.9%) were confirmed by the PRNT assay (21 from eastern Kenya). Two of the 21 PRNT-positive study subjects also had elevated IgM antibodies against RVFV suggesting recent infection. Multivariate modeling in this study revealed that being seminomadic (odds ratio [OR] = 6.4, 95% confidence interval [CI] = 2.1-15.4) was most strongly associated with antibodies against RVFV. Although we cannot know when these infections occurred, it seems likely that some interepidemic RVFV infections are occurring among herders. As there are disincentives regarding reporting RVFV outbreaks in livestock or wildlife, it may be prudent to conduct periodic, limited, active seroepidemiological surveillance for RVFV infections in herders, especially in eastern Kenya.

Elevated antibodies against Rift Valley fever virus among humans with exposure to ruminants in Saudi Arabia.

In 2000, an outbreak of Rift Valley fever virus (RVFV) occurred in the Kingdom of Saudi Arabia (KSA). Since then there have been sparse efforts to monitor for RVFV reemergence. During 2012, we enrolled 300 individuals with ruminant exposure and 50 age-group matched non-exposed controls in southwestern KSA, in a cross-sectional epidemiological study of RVFV. Sera from the participants were screened with an enzyme-linked immunosorbent assay (ELISA) for anti-RVFV IgG antibodies of which 39 (11.1%) were positive. Sixteen (41.0%) of those 39 were also positive by a plaque reduction neutralization assay (PRNT). The PRNT-positive subjects were further studied with an IgM ELISA and one was positive. No RVFV was detected in the 350 sera using real-time reverse transcription polymerase chain reaction. Contact with cattle (odds ratio [OR] = 3.16, 95% confidence interval [CI] 1.01, 9.90) and a history of chronic medical illness (OR = 6.41, 95% CI 1.75, 23.44) were associated with greater odds of RVFV seropositivity by PRNT. The IgM-positive participant was 36 years of age, and reported multiple risk factors for ruminant contact. Although these findings simply may be vestiges of the 2000 epidemic, KSA's frequent visits from pilgrims and importations of live animals from RVFV-endemic areas suggest that more comprehensive surveillance for imported RVFV virus in ruminants, mosquitoes, and travelers is imperative.