Fresh Nipah case surfaces in Kerala, 40-year-old man tests positive in Kozhikode

The story so far

Kerala ’s first encounter with Nipah virus (NiV) was in 2018, which identified 23 cases (including 18 lab-confirmed ones). The case fatality rate was 91% and there were two survivors. Since then, Kerala has recorded numerous spillovers of NiV.

In 2019, a lone case was identified in Ernakulam and the person survived the infection. In 2021, a 12-year-old boy was detected with the infection in Malappuram. In 2023, Nipah resulted in a cluster of six cases in Kozhikode. In 2024, two single cases each were reported from separate spillover events from Malappuram, in July and September of that year. In 2025, four cases of Nipah were reported from two districts, Malappuram and Palakkad and epidemiological investigations reported that none of these cases appeared to be linked to each other, suggesting independent spillover events from the natural reservoir.

NiV has resurfaced again in Kozhikode now and a 43-year-old, who tested positive for the virus, is battling for life at Kozhikode Medical College.

Why is Nipah recurring in Kerala?

Research has consistently identified the Indian flying fox bat ( Pteropus medius ) or the fruit bat as the natural reservoir of Nipah virus in Kerala. Serological studies and viral detection in bats have shown that the virus is circulating in bat colonies in the State, particularly in northern districts.

In the 2018 Kerala outbreak, about 25% of the sampled bats were found to be positive for Nipah viral RNA and in subsequent events too, bat samples had revealed the presence of NiV.

The Pteropus species are found across the State and very near human settlements. A mapping study of bat-roosting sites by Kerala Forest Research Institute’s Department of Wildlife Biology had found that almost all of the roosts were near human habitats, increasing the risk of zoonotic exposure.

The recurrent NiV spillovers in Kerala with fair regularity suggest that the virus has established itself in the environment. The peak Nipah virus spillover risk in the State is from April to September, when the abundance of seasonal fruit-laden trees, increased bat foraging activity, bat breeding season and viral shedding dynamics coincide, increasing the risk of human exposure. This pattern has not changed in Kerala since the very first outbreak.

Because of the perennial natural virus reservoir in the State, it might not be possible to prevent recurrent NiV spillover events in Kerala.

What makes Kerala particularly vulnerable to zoonotic diseases?

It is the convergence of ecological, demographic, climatic factors and increased human-wildlife interface that makes Kerala a special lab for zoonotic diseases.

The Western Ghats, which stretches along the State’s eastern flank, is one of the world’s richest biodiversity spots and the tropical rainforest climate sustains several hundred species of birds, reptiles and mammals. But only about 160,000 sq km of this rich biosphere is formally protected. The high population density in Kerala and the increased presence of human settlements, plantations, and agricultural lands immediately adjacent to and along the forest fringes increases the opportunities for human-wildlife interactions and facilitates exposure to novel pathogens.

Scientific literature links emerging zoonoses to deforestation, habitat fragmentation, urbanisation and agricultural intensification. When wildlife habitats are disturbed, the animals are forced into closer contact with human settlements and cultivated food sources. Scientists also warn that climate-related ecological disruptions could be important contributors to future spillover risk in the case of Nipah.

Nipah is just one among Kerala’s broader zoonotic risk profile, which includes other pathogenic diseases like Kyasanur Forest Disease (KFD), leptospirosis, scrub typhus, Japanese encephalitis, West Nile fever, rabies and avian influenza.

The World Health Organisation (WHO) has warned Kerala to be on the vigil about some high threat pathogens (HTPs) — Nipah, Avian Influenza (H5N1) and KFD — which have a high mortality profile and high transmissibility with pandemic potential.

How is Kerala responding to the recurrent threat of zoonotic events like Nipah?

Nipah has been classified by the WHO as a priority pathogen because of its lethality, unpredictability and its alarming potential to cause widespread outbreaks or even the next pandemic. The recurrent spillover incidents in Kerala has primed the health system about the importance of sharp and coordinated disease surveillance, rapid pathogen identification and containment efforts to ensure that human-to-human transmissions do not occur, resulting in a wide outbreak.

The 2018 brush with Nipah took the health system by surprise. Of the 23 cases identified in the outbreak, only the index case had contracted the infection in the community. All the remaining cases were due to nosocomial transmission in three different hospitals.

Kerala used the 2018 experience as an opportunity to develop a…