Nipah virus (NiV) is an emerging and serious viral zoonotic disease that carries with it a high case fatality rate (in the ballpark of 70% or more).
NiV is an enveloped RNA virus and along with Hendra virus make up the Henipahviruses.
The natural host of the virus are fruit bats of the Pteropodidae family, Pteropus genus.
According to the World Health Organization (WHO), there is no apparent disease in fruit bats.
It is assumed that the geographic distribution of Henipaviruses overlaps with that of Pteropus category. This hypothesis was reinforced with the evidence of Henipavirus infection in Pteropus bats from Australia, Bangladesh, Cambodia, China, India, Indonesia, Madagascar, Malaysia, Papua New Guinea, Thailand and Timor-Leste.
African fruit bats of the genus Eidolon, family Pteropodidae, were found positive for antibodies against Nipah and Hendra viruses, indicating that these viruses might be present within the geographic distribution of Pteropodidae bats in Africa.
It was first recognized in a large outbreak in Kampung Sungai Nipah, Malaysia and Singapore from Sep 1998 – May 1999.
276 cases were reported, the vast majority (93%) being pig farmers or people who had contact with pigs. The disease presented as encephalitis and four out 10 people died.
It is theorized that the pigs got infected consuming partially bat-eaten fruit that ended up in a pigsty. Pigs were the intermediate host in this case; however, subsequent outbreaks had no intermediate hosts.
No new outbreaks have been reported in Malaysia since 1999.
Outbreaks have occurred in India in 2001, 2007 (West Bengal) and 2018 (Kerala), while Bangladesh saw outbreaks/cases nearly every year from 2001-2015.
In fact, since NiV appeared in Bangladesh some 17 years ago, 298 cases and 209 deaths were reported (70% CFR). The Bangladesh cases were more respiratory issues than the Malaysia cases.
The outbreaks since the initial one in Malaysia have been linked to two possible routes of transmission—consumption of raw date palm sap that had been contaminated with urine or saliva from infected fruit bats and strong evidence points to human-to-human transmission (close physical contact, especially contact with body fluids).
Winter is “Nipah season” as this is the traditional date palm sap collecting time and this coincides with outbreaks.
What is date palm sap?
According to Bangladeshi officials, a cut is made in the stem of a date palm tree and the sap is collected in a container. The sap is consumed raw, fermented as an alcoholic beverage or boiled to form molasses.
Fruit bats also consume the date palm sap and can contaminate it with saliva, feces or urine.
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