Health employees wait to confess sufferers at a Nipah isolation ward on the Medical College, in Kozhikode on Friday.
| Photo Credit: PTI
Since May 2018 when Kerala reported the primary Nipah outbreak in Kozhikode district, there have been three extra outbreaks of Nipah virus together with the most recent one in late-August 2023. For causes nonetheless not identified, three of the 4 Nipah outbreaks in Kerala in 2018, 2021 and 2023 have been in Kozhikode district; the 2019 outbreak was in Ernakulam district.
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Even 5 years after the primary outbreak in Kerala, and 4 outbreaks in all, it’s nonetheless unclear why three of the 4 outbreaks have been in Kozhikode district in Kerala. Fruit bats that may trigger Nipah virus outbreaks in people are not restricted to Kozhikode district.
As per a 2021 research, Nipah virus was discovered to be in circulation in fruit bats (Pteropus species) in “many districts” in Kerala. An ongoing nationwide survey in 14 States by NIV Pune has discovered Nipah virus antibodies in fruit bats (Pteropus medius) in 9 States, together with Kerala, and the Union Territory of Pondicherry.
While date palm sap was linked to Nipah virus outbreaks in Bangladesh, and pigs performing as intermediate hosts have been chargeable for Nipah outbreaks in Malaysia, the route of virus transmission from bats to people has not been clearly established in Kerala.
The 4 outbreaks in 5 years could also be as a result of the virus has both turn into endemic in bats in Kerala or is a mirrored image of Kerala’s superior healthcare system that completely investigates undiagnosed fever instances for potential Nipah virus an infection or each. However, with fruit bats optimistic for Nipah virus antibodies being discovered in different States, it’s probably that Nipah virus an infection and deaths could also be going undetected in different States whereas they get picked up in Kerala, particularly in Kozhikode district.
“Whenever we have undiagnosed fever cases, a team involving virologists is formed and we undertake a detailed investigation which helps us diagnose Nipah virus and other new virus outbreaks early. In other States, Nipah cases might be going undetected,” says Dr. Anoop Kumar A.S., Director of Critical Care Medicine, North Kerala Cluster, Aster MIMS Calicut, Kerala. Dr. Kumar performed a pivotal position in detecting the Nipah virus outbreak in Kerala in 2018 and 2023. “Early lab confirmation, healthcare system acting fast and immediate public health response in Kerala has helped contain the outbreak quickly each time.”
In the 2019 and 2021 outbreak, there was only a single case with none human-to-human transmission. “Nipah virus infection and deaths might have happened in different parts of India in people with undiagnosed fever, which might have gone undetected. Also, there is no Nipah testing facility anywhere in India except NIV Pune. Only Kerala screens for Nipah virus routinely in a molecular lab in Calicut Medical College,” he says. “While other States may not be routinely sending samples for Nipah virus testing, we test for Nipah whenever there are cases with unusual symptoms. That might be the reason why Kerala is detecting Nipah cases.”
Usually, folks with Nipah virus an infection current with encephalitic signs. But in the most recent outbreak, sufferers introduced with pure respiratory signs, not reported wherever in the world earlier than. “But we could still identify them as Nipah only because we have a high index of suspicion,” says Dr. Kumar.
In 2018 and in 2023, the index case had died with encephalitis in 2018 and extreme pneumonia in 2023 that went unnoticed. In 2018, a cluster fashioned and Nipah virus was identified amongst three contacts who have been admitted with uncommon signs about two weeks after the dying of the index case. “There was a [possible] index case, clustering and unusual symptoms seen in the contacts. There was a high index of suspicion and that led us to diagnose Nipah virus in 2018,” recollects Dr. Kumar.
In the most recent outbreak too, there was a dying in one other hospital in Kozhikode metropolis on August 30 and 4 of the members of the family developed uncommon signs on September 9 and have been admitted two days later at Aster MIMS Calicut. Nipah virus was identified the very subsequent day after admission. “We noticed a clustering of cases after the death of the person. During a detailed history taking we came to know that the person who died had unusual symptoms. And the family was from a locality quite close (10-15 km) to the 2018 outbreak epicentre. There was a high index of suspicion of a new emerging virus or Nipah due to the combination of a [possible] index case, clustering of cases, unusual symptoms and proximity to the first outbreak epicentre. So we first tested for Nipah virus,” he says.
At the time the deaths occurred in the index case in 2018 and 2023, Nipah virus was not identified. In 2019 and 2021, only a single case was detected (ending in dying in 2021 not like in 2019). This raises the potential for a number of folks getting contaminated with Nipah virus and even dying with out a prognosis in different elements of Kerala and different States, particularly when only one or just a few instances happen, he says.
The Nipah virus has low infectivity (R0 of 0.2-0.3 in contrast with R0 of over 1.5 in the case of SARS-CoV-2 virus). “The infectivity from first-degree to second-degree patients is low when infected with Nipah virus but high in the case of index cases,” Dr. Kumar explains. In 2019 and 2021, the infectivity of even the index case might need been much less as that they had only encephalitis signs, which reduces the possibilities of virus unfold, he says whereas explaining why there have been no secondary instances then. Also, each Nipah virus index case needn’t transform a superspreader.
