4 Origin Scenarios if a Nipah Virus outbreak occurs outside South/SE Asia

Abstract

Nipah virus is a bat-borne zoonotic RNA virus discovered in Malaysia during an 1998-1999 outbreak that involved pigs, fruit bats, and humans in Malaysia (1). Clinical manifestations are primarily encephalitis and pneumonia. The case fatality rate of symptomatic cases is 40%-70%. Survivors can have severe neurologic sequelae (2-5). There are no licensed vaccines, antiviral drugs, monoclonal antibodies, or point-of-care rapid diagnostic tests, although extensive work on vaccines and monoclonal antibodies is underway (6). Person-to-person transmission, including a small number of superspreading events, has occurred in Bangladesh and India (7-9). From 1998-2023 all reported outbreaks have been in either southeast (SE) Asia (Malaysia, Singapore, the Philippines), or south Asia (Bangladesh, India) (2, 7-10). It is likely that a future Nipah outbreak, and possibly widespread epidemic, will occur outside south/SE Asia, whether elsewhere in Asia such as China, or on another continent. When it does, then as with the COVID-19 pandemic, multiple questions will be raised regarding the origin of the epidemic. Each of the following four (4) main scenarios could be anticipated to account for the origin of such a geographically-unprecedented Nipah epidemic during analysis on Day 1 of the event by national and international organizations.