The Nipah virus has been a recurring threat in Kerala, India, with the state reporting four cases, including two deaths, within a 50km radius in July 2025. As of now, 675 people are under surveillance across five districts. Let’s delve into what we know about the Nipah virus, its symptoms, and how authorities are working to contain it.
Nipah virus (NiV) is a highly pathogenic zoonotic virus that can be transmitted from animals to humans, causing death in 40 to 75 percent of human infected cases. Fruit bats of the Pteropodidae family are natural reservoirs of the virus. The spillover of the virus to humans can happen directly or via intermediate hosts such as pigs or horses.
Human NiV infections can range from asymptomatic infection to acute respiratory infection, seizures, and fatal encephalitis. The clinical presentation of NiV infection is neurological, affecting the central nervous system and resulting in acute encephalitis syndrome (AES). The incubation period of the virus is believed to be four to 14 days.
The first human NiV infection was recorded in 1998 in Malaysia and Singapore. Since then, outbreaks have occurred in Bangladesh, the Philippines, and India. Kerala has reported 10 instances of NiV spillover since 2018, with only two turning into outbreaks with instances of human-to-human spread. Authorities have been successful in containing the spread of the virus using trace-and-test procedures. Across 10 “spillover events”, the case count stands at just 37 infected individuals.
Thekkumkara Surendran Anish, nodal officer at the Kerala One Health Centre for Nipah Research and Resilience, emphasizes the importance of a strong surveillance system. “When a Nipah case is established, all primary contacts of the patient are immediately traced and monitored under house quarantine. If they test positive for the virus, we immediately start antiviral treatment.” The prophylactic treatment of primary contacts with broad-spectrum antiviral drugs has helped reduce mortality.
Currently, there are no approved treatment protocols for NiV, and doctors have used broad-spectrum antivirals like Ribavirin and Remdesivir. The University of Oxford’s NiV vaccine has begun in-human trials and was granted support from the Priority Medicines (PRIME) scheme of the European Medicines Agency (EMA) in June.
Anish highlights the importance of a “one health” approach to combating high-threat pathogens. “One health is a combination of three things – human health, animal health, and environment health. You have to tackle all these things to reduce the chances of zoonotic spillovers such as Nipah.” Ecological disruption, spread of human populations into wildlife habitats, and climate change are primary causes for the emergence of zoonotic viruses.