Carried by fruit bats, Nipah outbreaks often occur in Bangladesh between December and May - which is date palm sap harvesting season - as infected bats like to roost at night at the top of date palm trees, and collection containers can become contaminated with bat saliva and feces.
There are other routes of infection, as we saw in Malaysia in 1998 when the virus spread first from bat to pigs - and then from pigs to humans - eventually infecting at least 265 people, killing 105 (see Lessons from the Nipah virus outbreak in Malaysia).
Human-to-human transmission has also been reported, as in India in 2018 (see Nipah Transmission In Kerala Outbreak) where we saw apparently robust household and nosocomial transmission of the virus in Southern India, eventually infecting 19 people.
While the IEDCR hasn't updated its website/dashboard as of this writing, overnight there are numerous Bangladeshi media reports of two recent Nipah deaths. One such example comes from The Business Post, which describes 2 men (ages 38 and 27) who fell ill after consuming raw date juice, with both dying in a Dhaka hospital.
Nipah virus: 2 patients from Manikganj die in Dhaka
TBP Desk
29 Jan 2024 11:51:27 | Update: 29 Jan 2024 12:14:16
Two people from Manikganj, who were infected with Nipah virus after consuming raw date juice, died in Dhaka while undergoing treatment.
Given the limits of testing and surveillance, it is likely that some number of cases in Bangladesh, and in neighboring countries, go unidentified each year, as the geographic range of the fruit bat that carries the virus is quite large (see map below).
Outbreaks in humans since the virus was first identified in the late 1990s have tended to be sporadic, and small - with the Malaysian outbreak (1998-1999) being the largest. But in the 2013 paper The pandemic potential of Nipah virus, the author Stephen P. Luby wrote (bolding mine):
Characteristics of Nipah virus that increase its risk of becoming a global pandemic include:
After the 2018 outbreak in Kerala, India, concerns over larger, urban outbreaks of the virus have increased (see Enhancing preparation for large Nipah outbreaks beyond Bangladesh: Preventing a tragedy like Ebola in West Africa by Halsie Donaldson, Daniel Lucey).
- humans are already susceptible; many strains are capable of limited person-to-person transmission;
- as an RNA virus, it has an exceptionally high rate of mutation
- and that if a human-adapted strain were to infect communities in South Asia, high population densities and global interconnectedness would rapidly spread the infection.
Whether Nipah has - or will ever accrue - the `right stuff' to pose a genuine pandemic threat is unknowable, but it 2019 it ranked #20 in the CDC's list of Zoonotic concerns, well ahead of MERS-CoV (#27) and Mpox (#29).
Also in 2019 the WHO published their List Of Blueprint Priority Diseases, detailing 8 disease threats in need of urgent accelerated research and development. And Nipah, along with its Australian cousin Hendra, were among them.
Almost exactly a year ago, in EID Journal: Nipah Virus Exposure in Domestic and Peridomestic Animals Living in Human Outbreak Sites, Bangladesh, 2013–2015, we looked at a dispatch that described the detection of NiV antibodies in cattle, dogs, and cats in proximity to known outbreaks in humans
A reminder that while we continue to struggle with COVID, the next global health crisis may already be simmering in a bat, a rat, or a cat somewhere in the world, just waiting for the right conditions to allow it to start its world tour.While Nipah remains more of a regional concern than a global threat, each new human infection and every spillover event provides the virus with another opportunity to better adapt to a new host.
