Nipah test results of 13 people turn -ve, no new cases in state
Six people had displayed symptoms of Nipah virus infection, while three others were from the secondary contact list
Kerala breathed a sigh of relief on Monday after the results of the serum tests on 13 people who were in close contact with the 14-year-old boy from Pandikkad in Malappuram turned out to be negative for Nipah virus. The state had been on high alert since the boy died of Nipah virus at a Government Medical College Hospital in Kozhikode on July 21, marking the fourth outbreak of the deadly infection in six years.
Late in the evening, the National Institute of Virology (NIV) in Pune confirmed the findings of the tests carried out at the virology lab at Kozhikode Medical College.
Six people had displayed symptoms of Nipah virus infection, while three others were from the secondary contact list. The samples of the boy’s parents, who showed no symptoms, were also sent for testing.
The Kerala health department’s contact list includes 350 people, 101 of whom are in the high-risk category.
Health minister Veena George said that the list includes four people from Thiruvananthapuram and two from Palakkad.
The two people from Palakkad were workers at a private hospital, while the four from Thiruvananthapuram had travelled to Perinthalmanna in Malappuram district for treatment in the last three days. Besides, 68 people on the contact list are health workers, George said.
The authorities have identified the private bus on which the child travelled after being infected with the Nipah virus. A larger contact list is being prepared with the help of surveillance camera footage.
According to the minister, the boy who died of Nipah had eaten a hog plum (ambazhanga in Malayalam) from a plot infested with bats.
“The preliminary investigations show that this could be the source of infection,” she said. However, she said that further investigations were needed to confirm the source of the infection.
Meanwhile, a team of experts from the NIV reached Malappuram late in the evening to assess the situation. A team of scientists from the Indian Council of Medical Research (ICMR) had already reached the district.
According to the minister, parts of Kerala have been tagged as high-risk for the Nipah virus outbreak. The virus originates from fruit bats and animals like pigs and can cause a severe brain-swelling fever in humans.
The World Health Organization (WHO) classified the virus as a priority pathogen due to its potential to trigger epidemics. There is no vaccine yet to prevent Nipah virus infection, nor is there any specific treatment for it.
Across Malappuram, the state government has constituted 25 committees to identify and isolate affected individuals as part of the Nipah virus control measures.
In Malappuram and adjoining Wayanad and Kozhikode districts, ongoing monitoring over the next seven to ten days is emphasised. Isolation wards have been set up in healthcare facilities to manage potential cases, and family members of the affected patient have been placed under observation at a local hospital. Other individuals at risk have been advised to self-isolate at home.
Nipah outbreaks were reported in the Kozhikode district of Kerala in 2018, 2021, and 2023 and in the Ernakulam district in 2019. A total of 21 casualties have occurred as a result of Nipah, despite strong state measures to fight the spread. Bats in Kozhikode, Wayanad, Idukki, Malappuram, and Ernakulam districts had antibodies to the virus.
Kerala has been experiencing Nipah virus infections almost every year since 2018. As a result, local communities have been targeting bats, regardless of their species. However, scientists have pointed out that only the large fruit bats of the Pteropus genus are the natural reservoir of the virus.
Although pigs have been identified as another intermediate carrier, the areas where the disease has been reported do not have any pig farms or small-scale rearing of that animal. Despite the mass destruction of bat colonies across the state and the continuous study of samples at the National Virology Institute in Pune and other leading research centres, the bat connection to the spread of the zoonotic disease remains unconfirmed. Tested samples have debunked the popular assumption that bats were the sole carriers of the disease in Kerala.
A section of public health experts believe the panic now spreading in Kerala is a different variant of Nipah, and the source may not be bats, as in the case of northeastern states and Bangladesh, where it is being reported regularly.
The health department said it will continue testing bats and other animals. However, how the disease is transmitted from bats to humans remains unclear.
Though the Kozhikode-Malappuram region is home to a large population of fruit bats, experts believe various factors contribute to outbreaks in this area, including climate change, environmental degradation, and the characteristics of initial cases (the first people to contract the virus from animals).
“When Nipah was first reported in Malaysia in 1998, it was observed that bats affected by El Niño came closer to urban areas in large numbers. In Bangladesh and Bengal, the outbreak was linked to bat excreta. A clear connection is yet to be established in the case of Kerala outbreaks, but a common factor exists among the victims (index cases). They are all males, aged 12 to 25, who are active and adventurous,” explains Dr A Althaf, a public health expert and professor at Government Medical College Hospital in Thiruvananthapuram. He emphasised that establishing the epidemiological link requires continued efforts.
Malaria, amoebic meningoencephalitis, and now Nipah—Kerala has of late been witnessing outbreaks of several zoonotic diseases despite its long legacy of maintaining a quality public health system.
According to experts, dense forest cover, extreme climate changes, and the large migrant population make the state prone to such infections.
Dr Dipu T S, associate professor of infectious diseases in the Department of Internal Medicine at Amrita School of Medicine, warns that the risk of zoonotic diseases increases with greater human-animal interaction.
Deepu points out that the re-emergence of the Nipah virus suggests that the virus’s animal reservoir still exists.
As human-animal interaction grows, so does the likelihood of these viruses spreading from animals or birds to humans. Humans may lack natural immunity to viruses circulating among animals and birds.
Dr Dipu emphasises that diseases spread when boundaries between species are breached. He notes that, as an ecosystem, it’s not possible to eliminate these viruses and bacteria. However, he stresses the importance of caution to prevent the spread of these diseases.
Though there is a larger consensus in Kerala over the fight against Nipah, the state government’s inability to complete the works of the BioSafety Level 3 (BSL3) lab in Kozhikode, almost equal to the NIV in Pune due to fund constraints, is drawing criticism.
Its work started after the first outbreak, with the Indian Council of Medical Research giving a grant of ₹5.5 crore. Its completion needs to catch up as the state government requires ₹11 crore more to make it functional. Kozhikode witnessed protests against the government for not completing the lab and, as a result, waited many hours to get confirmation of the results from the Pune lab.
George said the worldwide mortality rate in the case of Nipah is 70%. In comparison, Kerala reduced it to 33% by targeting interventions all these years and making up the state’s entire health care system.
