While the bats did not test positive this time around, previously, evidence of the virus has been detected in dogs, cats, goats, sheep, and horses
The Indian Flying fox, a Pteropus bat. Photo: iStock No new Nipah virus cases were reported beyond September 15 after six cases, which included two deaths, were confirmed between September 12 and September 15 in Kerala’s Kozhikode district, a new report by the World Health Organization (WHO) said.
The remaining four patients remained clinically stable as of September 27, the WHO highlighted. Moreover, one patient survived despite being in intubation.
This indicates that these patients have improved and are recovering, Chandini Radhakrishnan, professor and head of the Department of Emergency Medicine at the Calicut Medical College based in Kozhikode, told Down to Earth (DTE).
She was part of the team at Kozhikode’s Govt Medical College Hospital which treated about 12 confirmed Nipah virus cases including the first case during the 2018 outbreak, the first of four outbreaks in Kerala.
Furthermore, the September outbreak reported a case fatality rate (CFR) of 33.3 per cent. In comparison, most previous Nipah virus outbreaks reported higher CFRs. In the 2018 outbreak in Kozhikode and Malappuram, a 91 per cent CFR was noted with 17 of the 18 confirmed case patients passing away.
The 2021 outbreak in Kerala observed a 100 per cent CFR, with the only patient afflicted with the disease not surviving.
During the first outbreak in West Bengal’s Siliguri, the CFR was 68 per cent among the 66 cases found. Subsequently, the CFR was 100 per cent when five Nipah virus cases were reported in 2007 in Nadia district, West Bengal.
However in 2019, the single case survived.
Radhakrishnan said a precise reason cannot be given as to why the CFR rate was below the typical range between 40 per cent and 100 per cent this year.
“Maybe the severity of the cases was different this time. It all depends on the viral load, the host, and the health system at large. Perhaps, there is more preparation after COVID-19,” she added.
The WHO report further confirmed that the virus found in Kerala is Indian Genotype or I-Genotype and is similar to the Nipah virus strain found in Bangladesh.
About 1,288 high-risk contacts and healthcare personnel were identified by September 27. They were all quarantined and under supervision for a period of 21 days.
As of September 27, all samples of bats, half-eaten fruits, and animal droppings collected on September 15 tested negative for the virus, and the origin so far remains unknown, the WHO report noted.
Samples were collected close to Kallad village falling under Maruthonkara Panchayat, and the nearby 121-hectare forest known to host several bat species.
The laboratory testing is being carried out by the Indian Council of Medical Research’s mobile BSL-3 lab, a field unit of the National Institute of Virology (NIV), both in Alappuzha and Pune.
While the bats did not test positive this time around, previously, evidence of the virus has been detected in dogs, cats, goats, sheep, and horses.
According to the WHO, eating fruits partially eaten by bats, and drinking raw date palm sap/toddy/juice are potential routes of transmission.
The Nipah virus is considered an emerging zoonotic disease of public health importance. It is particularly reported in areas where the Pteropus fruit bats can be found, within WHO’s Southeast Asia and the Western Pacific regions.
The outbreaks have a seasonal pattern, and generally occur either during the breeding season of the bats or the fruit harvesting season, with increased chances of the virus shedding in bats.
In 2018, of the 52 Pteropus bat samples collected from near the epicentre of the outbreak, 10 samples, or 19 per cent, tested positive for the virus. In another study by NIV, out of 36 Pteropus species bats tested for Nipah, 12 were found to be positive for antibodies against Nipah.
Similarly, samples were collected from 92 bats in 2019, and one rectal swab sample and three bats’ visceral organs were found positive. Serum samples of 52 bats were tested for anti-NiV Immunoglobulin (Ig) G antibodies, and 20.68 per cent tested positive.
Not just in Kerala, bats across the country have tested positive for the virus according to an ongoing nationwide survey by NIV. This is in nine Indian states and one Union territory. These are Kerala, Tamil Nadu, Karnataka, Goa, Maharashtra, Bihar, West Bengal, Assam, Meghalaya and Puducherry.
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