Survey found No Active Nipah Virus in West Bengal Bats, Antibodies Detected in One Specimen
A recent bat surveillance exercise conducted in parts of West Bengal has found no evidence of active Nipah virus infection, offering a measure of reassurance amid public health concerns triggered by confirmed human cases. However, the detection of antibodies in one bat has prompted authorities to continue monitoring, as it indicates prior exposure to the virus in local bat populations.
The survey, carried out jointly by state forest and health departments along with national virology experts, is part of a broader effort to trace possible sources of infection and prevent further transmission. Officials have stressed that while the findings reduce immediate concern, sustained vigilance remains essential given the serious nature of the disease.
Findings from the Bat Surveillance Exercise
According to officials involved in the operation, nine fruit bats were captured from the Kuberpur area along the Kolkata–Basirhat Road in Madhyamgram as part of the initial phase of the survey. Multiple samples were collected from each bat, including swabs and blood specimens, and tested using RT-PCR, the standard method for detecting active viral infection.
“All samples tested negative for the presence of the Nipah virus in West Bengal,” a senior forest department official said, adding that the results indicate there is currently no active circulation of the virus among the bats examined.
However, blood analysis revealed that one bat carried antibodies against Nipah. Health experts explained that antibodies suggest past exposure rather than an ongoing infection, meaning the bat was not infectious at the time of testing.
“This is a reassuring finding, but it does not allow for complacency,” a senior health department official said. “Surveillance and preventive measures will continue until we are fully assured there is no risk to the public.”
Context: Why the Survey Was Conducted
The Nipah virus in West Bengal bat survey was initiated after two confirmed Nipah virus infections were reported in the state, raising concerns about possible zoonotic transmission. Nipah virus is known to be carried naturally by fruit bats, which can transmit the virus to humans directly or indirectly through contaminated food items.
Health authorities were particularly focused on areas linked to suspected or confirmed cases. In Barasat and nearby localities, teams visited locations connected to a deceased woman who had developed Nipah-like symptoms in December but died before confirmatory testing could be completed. Family members reportedly told officials that she had consumed raw date palm sap prior to falling ill, a known risk factor in previous Nipah outbreaks.
Investigators also considered travel history and social interactions linked to confirmed cases, including visits to other districts, as part of their epidemiological assessment.
Role of Date Palm Sap and Human Exposure
Experts have repeatedly identified raw date palm sap as a potential route of Nipah virus transmission to humans. Fruit bats often feed on sap collected in open containers, and their saliva or urine can contaminate it. Humans who consume the sap without proper safeguards may be exposed to the virus.
As part of the ongoing investigation, samples of date palm sap collected from the surveyed areas were also tested. Officials confirmed that all samples examined so far have tested negative for the virus, reducing concerns of immediate foodborne transmission.
Nevertheless, health authorities continue to advise against consuming raw or unprocessed date palm sap, particularly during winter months when collection is common.
Scientific Collaboration and Ongoing Monitoring
The surveillance exercise is being conducted with the involvement of national-level research institutions specialising in virology and zoonotic diseases. Experts used geo-location data and field assessments to identify bat roosting sites near areas of concern, ensuring that sampling was targeted and scientifically informed.
Officials emphasised that the current findings are based on a limited sample size and represent only one phase of a broader monitoring programme. Additional surveys and testing may be carried out in other locations if required.
“Detecting antibodies tells us the virus may have circulated in the past, which is not unusual in bat populations,” an official associated with the survey said. “The key point is that there is no evidence of active infection right now.”
Public Health Measures and Advisory
State health authorities have continued to strengthen surveillance in hospitals and communities, particularly among healthcare workers and close contacts of confirmed cases. Infection control protocols, contact tracing, and awareness campaigns are being reinforced to ensure early detection of any new cases.
Doctors and public health experts have reiterated that Nipah virus does not spread easily among humans without close contact, but when it does, it can cause severe illness. Early identification, isolation, and supportive care remain critical to reducing fatalities.
Conclusion
The absence of active Nipah virus in West Bengal bats sampled during the recent survey offers reassurance at a time of heightened concern. At the same time, the detection of antibodies in one specimen underscores the importance of sustained monitoring, as fruit bats remain a natural reservoir of the virus.
Authorities have indicated that surveillance efforts will continue, alongside public advisories and preventive measures, to minimise the risk of future outbreaks. As health officials balance caution with clarity, the focus remains on preparedness, early detection, and community awareness to safeguard public health in the months ahead.
