Explained | Why is Nipah’s return in Kerala a cause for concern?

How does Nipah spread? Is there a cure for this ‘emerging zoonotic disease’?

The virus takes from 6 to 21 days to incubate and manifest as disease.

The story so far: Kerala has reported a

fatality from a case of infection by the

Nipah virus in the northern district of Kozhikode bringing back memories of the chaos in

May-June 2018 when the same district reported 18 confirmed cases of which there were 17 laboratory-confirmed deaths. It’s the high mortality associated with the virus that triggered panic across the State and the country and when it was controlled the State’s healthcare surveillance system came in for praise though, as it turned out, it was only a test-run for the pandemic of 2020. This time, of the 274 people identified as being among the primary contacts of the 12-year-old boy who died, 68 have tested negative. Close to 15,000 people who live within a three-kilometre radius of the boy’s family, too, are being surveyed for symptoms.

Have outbreaks been frequent?

The human Nipah virus, as it is called, is classified as an “emerging zoonotic disease”, meaning that it can transfer to people after being incubated in other species. It was first recognised in a large outbreak of 276 cases in Malaysia and Singapore from September 1998-1999.

Editorial | Nipah amidst a pandemic

Prior to the Kerala outbreak of 2018, there have been several Nipah virus outbreaks in Bangladesh with spillovers into India

particularly in 2001 and 2007 at Siliguri and Nadia in West Bengal. During the outbreak in Siliguri, 33 health workers and hospital visitors became ill after exposure to patients hospitalised with Nipah virus illness. At least 70 people died in the outbreaks in these two districts. In the 2018 outbreak in Kerala , four from the family of the first person confirmed with the infection succumbed to the viral disease.

Where does the virus originate?

The Nipah virus (NiV) is classified as a “highly pathogenic paramyxovirus”, and handling it requires the highest grade of facilities called BS-4. The natural reservoir for the virus is large fruit bats of the Pteropus genus. From here the virus may pass on to pigs which may be infected after eating fruits that are bitten on by infected bats. It’s also possible for the virus to have jumped to humans from bats without pigs being involved, as in previous outbreaks in Bangladesh, via direct contact or through fruits contaminated by bats. Kerala has several fruit plantations that host several species of bats. While investigations are on to determine if there are infected bats in the districts, so far no evidence has emerged. In 2018 too, the animal source of the virus wasn’t established. The virus takes 6-21 days to incubate and manifest as disease. Unlike in the case of the coronavirus which is airborne and can spread across great distances, Nipah does not transmit efficiently. Contact with body fluids and an infected person’s respiratory droplets are the most common ways to catch an infection which explains why those who share a house or hospital facilities harbouring the infected patients are at the greatest risk.

What are the symptoms and how is it diagnosed?

Fever, delirium, severe weakness, headache, respiratory distress, cough, vomiting, muscle pain, convulsion and diarrhoea are the main symptoms. Inflammation of the brain (encephalitis) or respiratory diseases are common too, hence the 40%-75% fatality rate. Because of the lethality of the virus, very few Indian laboratories like the Pune-based National Institute of Virology are equipped to isolate the virus using cell culture methods. However, the virus’s presence in blood or saliva samples can be determined — like coronavirus tests — in commercial antibody tests that detect the presence of antibodies in the serum. Tests like RT-PCR, undertaken by commercial laboratories, can also be used to detect the virus.

What is the treatment protocol?

Currently, there is no known treatment or vaccine for either people or animals. Ribavirin, an antiviral, may have a role in reducing mortality among patients with encephalitis caused by the Nipah virus disease, according to a fact-sheet by the National Centre for Disease Control. The thrust of treatment relies on managing symptoms. There are, however, immunotherapeutic treatments (monoclonal antibody therapies) that are under development and evaluation. One such monoclonal antibody, m102.4, has completed Phase 1 clinical trials, and has been used on a compassionate use basis. In addition, the antiviral treatment Remdesivir has been effective in non-human primates when given as post-exposure prophylaxis, according to the U.S. Centers for Disease Control and Prevention. There are no approved vaccines but recent studies have shown that

a Covishield-like vaccine fully protected a small group of primates (Green African monkeys). Another vaccine candidate has been in preliminary human trials, with the results expected later this year.

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