Nipah virus

The outbreak was originally mistaken for Japanese encephalitis, but physicians in the area noted that persons who had been vaccinated against Japanese encephalitis were not protected in the epidemic, and the number of cases among adults was unusual.^[20] Although these observations were recorded in the first month of the outbreak, the Ministry of Health failed to take them into account, and launched a nationwide campaign to educate people on the dangers of Japanese encephalitis and its vector, Culex mosquitoes.^{[citation needed]}

Symptoms of infection from the Malaysian outbreak were primarily encephalitic in humans and respiratory in pigs. Later outbreaks have caused respiratory illness in humans, increasing the likelihood of human-to-human transmission and indicating the existence of more dangerous strains of the virus.

During the 1999 outbreak of Nipah virus, which occurred among pig farmers, the majority of human infections stemmed from direct contact with sick pigs and the unprotected handling of secretions from the pigs.

Based on seroprevalence data and virus isolations, the primary reservoir for Nipah virus was identified as Pteropid fruit bats, including Pteropus vampyrus (large flying fox), and Pteropus hypomelanus (small flying fox), both found in Malaysia.^[21]

The transmission of Nipah virus from flying foxes to pigs is thought to be due to an increasing overlap between bat habitats and piggeries in peninsular Malaysia. In one outbreak, fruit orchards were in close proximity to the piggery, allowing the spillage of urine, faeces and partially eaten fruit onto the pigs.^[22] Retrospective studies demonstrate that viral spillover into pigs may have been occurring, undetected, in Malaysia since 1996.^[15] During 1998, viral spread was aided by the transfer of infected pigs to other farms, where new outbreaks occurred.^[14]

Future threat

The Nipah virus has been classified by the

Presently, there are no dedicated drugs or vaccines available for the treatment or prevention of Nipah virus infection. The World Health Organization (WHO) has designated Nipah virus as a priority disease within the WHO Research and Development Blueprint. In cases of severe respiratory and neurological complications resulting from Nipah virus infection, healthcare professionals advise intensive supportive care as the primary treatment approach.[14]

In January 2024 a candidate vaccine, ChAdOx1 NipahB, commenced Phase I clinical trials after completing laboratory and animal testing.^[26][27]

Outbreaks of disease

Nipah virus infection outbreaks have been reported in Malaysia, Singapore, Bangladesh and India. The highest mortality due to Nipah virus infection has occurred in Bangladesh, where outbreaks are typically seen in winter.^[28] Nipah virus first appeared in 1998, in peninsular Malaysia in pigs and pig farmers. By mid-1999, more than 265 human cases of encephalitis, including 105 deaths, had been reported in Malaysia, and 11 cases of either encephalitis or respiratory illness with one fatality were reported in Singapore.^[29] In 2001, Nipah virus was reported from Meherpur District, Bangladesh^[30][31] and Siliguri, India.^[30] The outbreak again appeared in 2003, 2004 and 2005 in Naogaon District, Manikganj District, Rajbari District, Faridpur District and Tangail District.^[31] In Bangladesh there were also outbreaks in subsequent years.^[32] In September 2021, Nipah virus resurfaced in Kerala, India claiming the life of a 12-year-old boy.^[33] The most recent outbreak of Nipah virus occurred during January and February 2023 in Bangladesh with a total of 11 cases (ten confirmed, one probable) resulting in 8 deaths, a case fatality rate of 73%.^[34] This outbreak resulted in the highest number of cases reported since 2015 in Bangladesh, and ten of the 11 cases during the 2023 outbreak had a confirmed history of consuming date palm sap.^[34]

See also

• 1998–1999 Malaysia Nipah virus outbreak
• Nipah virus outbreaks in Kerala

References