Why is Nipah virus a recurring phenomenon in Kerala?

Kerala has experienced its fourth outbreak of the zoonotic virus Nipah in the past five years, which first struck the state in 2018 and claimed 17 lives.

In an interview with The Indian Express, Dr A S Anoop Kumar, a specialist in infectious diseases and tropical fevers, compares the recent cases with the 2018 outbreak in Kerala.

In 2023, six cases have already been found, all of which are located in Kozhikode, a district in northern Kerala.

On both the occasions, Dr Anoop played a key role in the timely detection of the virus and containment of the outbreak.

Dr Anoop, Director of Critical Care for the North Kerala Cluster of Aster MIMS Hospital, had also participated in the Covid-19 expert advisory panel for the state government.

Dr Anoop says it was proven that bats in the Kozhikode area have the Nipah virus during the 2018 outbreak.

The virus strain was then isolated from all of the cases, proving that bats are the source of infection. One explanation for the virus' recurrent appearance could be due to this, he added.

He also mentioned that other states also have presence of bats, but they do not report any Nipah cases as they don’t have a higher index of suspicion. However, in Kerala, we take all necessary precautions, gather samples, and identify cases even if we have a passing suspicion that there may be an infection.

“All fruit bats in India are reservoirs of the Nipah virus” Dr Anoop said to the publication.

According to him, Kerala "suspects" more Nipah cases for a variety of reasons, including the state's more advanced healthcare system and its inhabitants' increased awareness. 

Comparing the Nipah virus symptoms in 2018 to those of 2023, he said that all of the patients during the Kerala outbreak in 2018 had symptoms of encephalitis; they arrived at the hospital with a fever and later experienced unconsciousness and neurological problems. The patients have primarily displayed respiratory symptoms this time and have developed severe pneumonia. They did not have many encephalitis symptoms, he added. 

Dr Anoop  said that Nipah virus transmission is not airborne, but mostly droplet-based. Thus, if there is proper infection control practice, there is a low possibility of virus transmission in hospitals. However, this time, there may have been a breach in infection control procedures that allowed one health worker to become infected and another to contract the illness from a hospital.

“After the Covid-19 pandemic, the system is very smooth in handling such outbreaks. Now, health workers are used to handling a high-priority viral pathogen with all precautions,” Dr Anoop added.