In the midst of a global pandemic that has infected almost 100 million people, Asia could soon be facing another emerging virus threat with a far higher death rate. Nipah virus, an RNA virus that originating in bats much like SARS-CoV-2, has caused many outbreaks throughout Malaysia, Singapore, India, and Northern Australia over the past 20 years. Now virus researchers are warning it has the potential to affect many more people if lessons aren’t learned from the outbreak of COVID-19.
Nipah virus was first recognized in 1999 after an outbreak in Malaysia. During the outbreak, 265 cases of acute encephalitis were noted, which started off in pig farms. The cases were originally attributed to Japanese encephalitis, but it was correctly identified as Nipah virus infection shortly after. Since then, small outbreaks have occurred almost yearly from 2000-2020, each time exhibiting an astonishing mortality rate of up to 75%.
Many will wonder why a virus with such extreme mortality rates is considered a pandemic risk – usually, diseases like this kill their hosts too rapidly to transmit effectively enough for a widespread threat.
However, this is where Nipah virus differs from many other viruses. While symptoms usually occur between 4-14 days after infection, sometimes the virus can incubate for extreme lengths of time – up to 45 days, according to the WHO – allowing for a remarkably long period to transmit.
Once incubation is over, symptoms include fever, headaches, and vomiting, amongst others that are akin to influenza infection. These are subsequently followed by dizziness, neurological symptoms, and acute encephalitis. Although various antiviral treatments are used as a supportive treatment for patients, there is no cure and no direct treatment against the virus as of 2021. If patients survive, some are left with long-term neurological problems, including personality changes and seizures.
Whilst still a significant threat, current strains of Nipah virus cannot be transmitted by aerosol, nor are they airborne, so likely won’t pose the same level of pandemic risk that viruses such as SARS-CoV-2 do without genetic changes that enable increased transmission. Currently, Nipah virus is spread largely through the ingestion of contaminated food that has been in contact with infected fruit bats, although infected pig feces and even human-to-human transmission has been observed.
Study and further analysis of viruses such as Nipah will enable the world to be better prepared for emerging virus threats. With COVID-19 running rampant through so many nations, understanding existing diseases that could cause similar devastation is paramount – particularly in how the world protects against viruses transmitted by bats, suggests virologist Veasna Duong.
"Sixty percent of people we interviewed didn't know that bats transmit disease. There is still a lack of knowledge," says Duong in an interview with the BBC.
"We observe [fruit bats] here and in Thailand, in markets, worship areas, schools and tourist locations like Angkor Wat – there's a big roost of bats there," he says. According to the BBC, "In a normal year, Angkor Wat hosts 2.6 million visitors: that's 2.6 million opportunities for Nipah virus to jump from bats to humans annually in just one location."
Experts now warn that COVID-19 should serve as a wake-up call for nations around the world to prepare for and prevent future outbreaks.