Epidemiology

Outbreaks of Nipah virus (NiV) have occurred in Bangladesh almost annually since 2001, particularly in winter months during the date palm sap harvesting period.[5][6] Other countries where NiV outbreaks have occurred include Singapore and Malaysia (where the virus was first discovered in 1998-1999), India, and the Philippines (this was a probable NiV outbreak).[7][8][9][10][11] An isolated case was reported in India, Kerala state, in September 2021.[12] NiV has never been reported in a traveller.

Hendra virus (HeV) outbreaks have thus far only occurred in Australia, with a total of 7 human infections (as of August 2022) since its emergence in 1994, all involving direct contact with horses.[13]

The natural hosts of both NiV and HeV are Pteropus bats. Human outbreaks occur when the virus is transmitted from bats to humans either directly or indirectly via intermediate hosts. Pteropus bats have a widespread geographical distribution, from Southeast Asia and northern Australia through to West Africa.[14] Therefore, there is a potential for henipavirus outbreaks in other countries where not previously reported. In support of this, a surveillance study in Africa identified people who were seropositive for neutralising antibodies to henipaviruses. Butchering bat meat was associated with seropositivity.[15]

A phylogenetically distinct henipavirus, Langya henipavirus (LayV), was identified in a throat swab sample in one patient in China in 2018 during sentinel surveillance of febrile patients with a recent history of animal exposure. Since then, 35 patients with acute LayV infection have been reported in the Henan and Shandong provinces between December 2018 and mid-2021. Most patients presented with a mild influenza-like illness, and there were no deaths. Findings suggest that LayV was the cause of the febrile illness as it was the only potential pathogen detected in 74% of patients. The majority of patients were farm workers, and it has been suggested that shrews may be the natural animal reservoir. Contact tracing of 9 patients with 15 close-contact family members revealed no close-contact transmission, and no cases of human-to-human transmission have been reported.[16] Further research is required.

Use of this content is subject to our disclaimer