What is Nipah virus and what we know about its recent outbreak in Kerala

Members of a medical team from Kozhikode Medical College carry areca nut and guava fruit samples to conduct tests for Nipah virus in Maruthonkara village in Kozhikode district, Kerala, India on September 13, 2023. Image: Reuters/Stringer

The state of Kerala is currently battling a fourth outbreak of the Nipah virus (NiV), causing two deaths, on August 30 and September 11. The resurgence of the virus is being reported from the Kozhikode district, with the authorities declaring containment zones in at least eight of its villages. The total tally of infected people stood at six at the time of publishing this story. 

In 2018, when the virus was first reported in Kerala, it claimed 21 lives out of 23 infected. The following outbreaks took place in 2019 and 2021, with two people dead, per Reuters.  

What is the Nipah virus?  

The World Health Organization describes NiV as a zoonotic virus as it can transmit from animals to humans.  

It was first recognised in 1999 during an outbreak among pig farmers in Malaysia but no new outbreaks have been reported from the country since. Four other countries have witnessed outbreaks including Singapore, Bangladesh, Philippines, and India. As per the US-based Centers for Disease Control and Prevention, outbreaks occur almost annually in Asia, especially in Bangladesh and India.  

It can spread to people from being in direct contact with infected animals such as bats, pigs, or their body fluids. It can also be passed on through contaminated food or directly between people.

What we know about the current strain  

The government of Kerala claims that the current strain being seen in the state is the Bangladesh variant. Although health officials say it is less infectious, it has the potential to spread from human to human. It also has a high mortality rate because there is no medicine or vaccine to treat the infection making preventive care and management of symptoms the only possible treatments available.  

Also read: Dr Priya Abraham: For the love of virology

The steps taken so far  

On Thursday, September 14, the Indian Council of Medical Research (ICMR) delivered the antibody requested to combat the virus, and a mobile laboratory was also sent to Kozhikode to test samples, according to PTI. This antiviral is the only treatment available to treat infections. However, its efficacy has not been clinically proven yet.  

A five-member team comprising experts from the National Centre for Disease Control, RML Hospital, and NIMHANS has been deployed in Kerala to keep tabs on the situation and assist authorities in containing the virus.  

According to Hindustan Times, the contact list contains 950 people, with 213 people belonging to the high-risk category.  

Schools, colleges, tuition, and coaching centres in Kozhikode will remain shut till September 17. Friday prayers on September 15 at Kozhikode's Kuttiady Juma Masjid will also not be held.

Authorities have also asked people to avoid consuming liquor collected in open vessels from palm trees.  

Also read: 827,000 undiscovered viruses in animals, birds have the ability to infect humans

Why Kerala often reports viruses first  

According to an investigation published by Reuters in May 2023, Kerala, with a sizeable forest cover and a severe monsoon pattern, is witnessing urbanisation at a fast pace. With rapid tree loss and shrinkage of natural habitats, animals’ proximity to human settlements is one of the factors responsible for successive zoonotic outbreaks. Climate change is another.  

Other reports also attribute the phenomenon to the large-scale migration that takes place from states such as Uttar Pradesh, Punjab, and Kerala of people in search of jobs and livelihoods who unknowingly end up becoming carriers of diseases.  

However, experts have often lauded Kerala’s robust surveillance system. The WHO has also praised the state for its active reporting of Covid-19 cases and managing to curb numbers during the initial outbreak of the virus.  

Additionally, the state’s high literacy rates, even in remote villages, contribute to early detection and effective management of diseases given they know the importance of reporting symptoms to ASHA workers and women's self-help groups.  

Also read: As India stumbles, one state charts its own Covid-19 course

Signs and symptoms of the Nipah virus  

The WHO has stated that an infection in humans may be asymptomatic, and could result in acute respiratory infection and fatal encephalitis (inflammation of the brain).  

Infected people may initially develop symptoms such as fever, headaches, myalgia or muscle pain, vomiting, and sore throat. Encephalitis and seizures occur in severe cases.  

The incubation period or the period between the infection to the onset of symptoms may range between four and 14 days. Fatality rates range between 40 percent and 75 percent.  

Prevention  

The CDC mentions avoiding areas where bats are known to roost; drink, or eat products that could be contaminated by bats, such as raw fruit or fruit fallen on the ground, and practising handwashing regularly as some precautionary measures.