Nipah virus carried by bats could become a new scourge in India

Indian health authorities are sounding the alarm after dozens of people were infected and a 12-year-old boy died from the Nipah virus, for which there is currently no vaccine. So what do we know about the outbreak?

A team of specialists was sent to the southern state of Kerala to assist local medics after samples taken from the deceased child tested positive for the Nipah virus. Before he passed away Sunday, the boy had symptoms of brain and heart muscle inflammation — conditions known as encephalitis and myocarditis.

To date, 11 people in Kerala have been diagnosed with the rare zoonotic virus. Among them are the boy’s parents, his relatives and some of the medics who treated him. More than 250 others have been identified through contact tracing, with 54 of them in the high-risk category, who have been instructed to self-isolate.

How dangerous is Nipah virus?

The World Health Organization (WHO) estimates a mortality rate of 40% to 75%, depending on the effectiveness of the health care system in the affected region. In contrast, the mortality rate for Covid-19 is 1% to 2%, according to global data, although it is more contagious.

Nipah causes an acute respiratory infection with fever, headache, muscle pain, vomiting, and sore throat. In severe cases, encephalitis develops, which can lead to coma and death. The lack of specific symptoms in the early stages makes it difficult to detect nipah, which often leads to delays in control measures and, therefore, even more infections.

Where does it come from?

The virus gets its name from the Malaysian village of Nipah, where the first outbreak among pig farmers occurred in 1999. Since then, there have been no new cases in Malaysia, but in Bangladesh, outbreaks have been an annual problem since 2001. Infections have also been detected intermittently in India. The hosts of the virus are believed to be fruit bats, known as flying foxes, which form large colonies in tree tops throughout South and Southeast Asia, often near populated areas.

How does it spread?

People usually contract the virus by eating fruit or drinking the raw sap of the bats’ favorite tree, the date palm, which has been contaminated with the saliva or urine of sick flying foxes. Pigs, horses, goats, sheep, cats and dogs can also serve as intermediate hosts. Unlike Covid-19, which can be spread by airborne droplets, Nipah is transmitted from person to person by close contact, through secretions and excretions, so relatives of infected people and health care workers caring for them are usually among the first to be infected. During the previous outbreak in Kerala in 2018, the R-number of Nipah – the “multiplication” rate that shows how many people one sick person can infect on average – was 0.43, while the R-number of coronavirus is estimated to be more than 1. An R-number below 1 means that the infection will eventually die out.

What is the treatment?

The WHO has identified Nipah virus as a priority disease for research and development, but there are currently no drugs or vaccines specific for the virus. It recommends only intensive therapy to treat those suffering from severe respiratory and neurological complications. Indian authorities ordered monoclonal antibody drugs from Australia that helped contain the outbreak in Kerala three years ago, and local health officials have also found that the antiviral drug ribavirin effectively reduces the viral load in patients with Nipah virus.

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