All Four Cases of Nipah Infections Are Each Other’s Contacts : Kerala Epidemiologist

New Delhi: As Kerala undergoes the fourth outbreak of Nipah virus since 2018 which has already killed two and infected two more, the state government has kicked in protocols to make containment zones in Kozhikode district. The Union government has also sent an Indian Council of Medical Research (ICMR) team to the state. The village panchayats, where these four lived, have also stepped up surveillance. 

Talking to The Wire, state epidemiologist Dr. Hari Shankar said all the four people who have tested positive are related to, or are contacts of the index(first) case. This explains how the virus can spread between humans, once it enters the human chain. Besides the four known cases, there are two more suspected ones, he said. He added that contact tracing is still going on. 

“Since out of the four, two are still undergoing treatment [and two have died], we are speaking to their relatives to trace the history of their whereabouts for at least the last two weeks so that further spread of the virus can be stopped,” he added.

Kerala experienced its first-ever and the worst outbreak of the Nipah virus in Kozhikode in 2018, when of the 23 infected, only two people survived. In that outbreak too, the majority of them were related to the index case. The second and the third outbreaks were far less deadly than the first one. In 2019, one boy from Ernakulam district reported positive for the virus but no death took place. In 2021, one died in the outbreak in Kozhikode. 

Also read: How Kerala Passed the Tough Nipah Test

In a paper published in 2021, the researchers of National Institute of Virology (NIV) wrote that they had found that Pteropus medius bats, or what are also known as the Indian fruit bats, were harbouring the Nipah virus. And, the spillover to the lone Nipah case of the 21-year-old boy in 2019 happened from the animal only. 

To know what led to the spillover this time, ICMR and National Institute of Virology researchers are expected to arrive in Kerala soon, the state epidemiologist said. 

In the paper, the researchers said that the Nipah virus was going to stay in the state. “NiV [Nipah virus] Positivity in Pteropus species of bats revealed that NiV is circulating in many districts of Kerala state, and active surveillance of NiV should be immediately set up to know the hotspot area for NiV infection.”

The Kerala government was nonetheless able to limit the spread of the virus to a great extent in 2019 and 2021 taking lessons from the 2018 outbreak after the spillover events from animals to humans. 

According to the World Health Organisation, the virus is mostly found in bats or pigs. 

“If the NIV/ICMR scientists are able to pinpoint the details of the spillover event this time, it would help us take precautionary measures,” Dr. Shankar said. Although it is not an easy task to do. 

According to the Indian Express, the areas under surveillance in the current outbreak are two villages in the eastern region of the Kozhikode district. Both the villages are situated 15 km away from Changaroth, where the deadly outbreak of 2018 happened. The region has dense forests where these bats are mostly found.

Dr. Shankar said, on the evening of September 12, that it was not clear at the moment as to which of the two strains of the virus – Malaysian or Bangladeshi – was currently in circulation. “The results of the genome sequencing, done to know this, are still awaited,” he said. Incidentally, all three previous outbreaks were related to Bangladeshi strain.

According to the WHO, there are mostly two strains of the virus – Bangladeshi and Malaysian. 

“During the first recognized outbreak in Malaysia [in 1999], which also affected Singapore, most human infections resulted from direct contact with sick pigs or their contaminated tissues. Transmission is thought to have occurred via unprotected exposure to secretions from the pigs, or unprotected contact with the tissue of a sick animal,” the WHO says.

In Bangladesh, the consumption of certain fruits or fruit products, which have been contaminated with saliva or secretions of fruit bats, that harboured the virus, led to the outbreaks. In all the previous three outbreaks of the virus in Kerala, fruit bats have been identified as the source which breed between July and October, and thus the chances of them infecting raw fruits become higher in this season.

As for the symptoms, they are mostly respiratory. And, therefore, the spread from one person to another is quite noticeable unless the containment measures are not quickly put in place. Some patients also develop neurological complications which may lead to death. Those who died in the current outbreak had both neurological and respiratory symptoms, the state epidemiologist said. While one died on August 30, the other passed away on September 11. 

Just like the vaccine, there is currently no proven treatment for the disease per se, according to the WHO. The symptomatic treatment is, however, available although the state epidemiologist said they are using antivirals and monoclonal antibodies to treat those infected.