After third instance of Nipah, experts say no proof to link bats in Kozhikode to virus

Seven kilometres away from the town of Kuttiadi in north-east Kozhikode is the Janaki Forest, spread over 135 hectares -- so named because the land once belonged to VK Janaki Amma, sister to renowned politician and diplomat VK Krishna Menon. Placed in the Maruthonkara panchayat, it is in the vicinity of where the Nipah virus has once more emerged in Kerala, five years after the first occurrence that took 17 lives and left the whole state petrified. Recurrences in the years in between had not been so deadly and COVID-19 had overshadowed memories of Nipah. But the resurgence in September, together with the news of two deaths once again in Kozhikode, raises questions of its apparent affinity to this one area.

Anoop Kumar AS, the doctor who made the connection between the symptoms and the viral disease in 2018 and again in 2023, told TNM that the area that the infected family came from was a red flag. Until then, three children and their 25-year-old relative who were admitted with a fever had tested negative for every other viral infection. But when the doctor learned that the family came from Maruthonkara and the father of two of the kids had died of symptoms including blurred vision, he had them tested for Nipah. The results of one of the kids, aged nine, and the 25-year-old relative came positive. As of Monday, September 18, there are four positive patients under treatment and two deaths.

Nipah is a zoonotic virus, it comes to humans through animals. Bats and pigs are known carriers, so are food contaminated by either. After the first human infection, the disease can pass on from person to person. When Nipah first came to Kerala, bats in Janaki Forest in Maruthonkara had tested positive for the virus, Dr Anoop remembers. But he is the first to disband any connection to Kozhikode or Maruthonkara as the only origin of the disease. He and other experts remind you that the Nipah virus is a natural host in fruit bats in almost every state of India. “They have co-evolved,” says PO Nameer, head of the Centre for Wildlife Studies, Kerala Agriculture University. It is not a big deal, finding the virus in bats, he says.

“What you need to find is how the virus spread from the bat to humans. There is no relation between the Nipah infections and the Janaki Forest unless you can prove that and establish that these bats are in the forest,” Nameer says.

Pteropus medius or flying fox or more commonly known as the fruit bat is not a forest species, he says. It lives in human dominated landscapes. It has also been said that the index patient Mohammed Ali had not gone to the Janaki Forest at the time of his infection. Sajith K, panchayat president of Maruthonkara, says that Mohammed Ali had gone to work in the fields near his house and in a neighbouring panchayat two days before he started having a fever. “Janaki Forest has bats but there is no chance of him having come into contact with them in recent days. On the other hand, there could have been bats in the fields he visited since it is all hilly areas here,” Sajith says.

Deepesh, who works in the ecotourism centre of Janaki Forest, says that there has been no such report of bats from the area causing the infection, though teams of experts have been visiting to study the forest after the outbreak.

“Flying foxes can easily cover 50 km or more during a night's feeding, so if the infections in fact came from bats, there would be a wide range of possible origin,” points out Merlin Tuttle, American ecologist specialised in bat behavior and conservation. He argues that the testing for Nipah has been heavily biased towards bats with little attention paid to other potential animal hosts.

“You might go so far as to ask if live Nipah virus has ever been isolated from a wild caught bat. As in the case of MERS and Ebola, bats were wrongly blamed. MERS comes from camels and Ebola apparently from great apes, or from undetected asymptomatic humans,” Merlin says.

Unlike in Malaysia and Bangladesh – two countries where the Nipah outbreak had previously occurred – no connection has been established in Kerala, between the origin of the disease and the first affected human. In Malaysia, the virus had spilled from pigs to bats to humans. In Bangladesh, it was toddy, contaminated by bats, that brought the infection to humans. In both these cases, there have been multiple infections at the same time, as opposed to the case in Kerala when it began with a single index patient, says Dr Arun Zachariah, chief veterinary surgeon, Kerala Forest Department.

It was suspected that the first infections in Kerala may have come from the consumption of mangoes bitten by fruit bats. Again, no proof was found.

To find out the connection between the animal source and humans, you need to look into the environment, food and the pathogen, Dr Arun says.