The southern Indian state of Kerala is on alert following two deaths from an outbreak of Nipah virus, with hundreds of people subjected to testing.
Seventy-seven of the contacts have been identified as “high risk” and have been asked to isolate at home with close monitoring of their health. Three people, including a child, who tested positive for the virus were hospitalized for observation.
Nipah is a zoonotic virus, meaning that it can spread between animals and people. Infection can be prevented by avoiding exposure to sick bats and pigs, avoiding places where the virus is present, and not drinking the sap of raw date palm, which can be contaminated by an infected bat. There’s no vaccine for the Nipah virus.
Nipah is estimated to kill 40 to 75 percent of infected individuals, which is far higher than COVID-19’s fatality rate of about 2 percent.
In the district of Kozhikode, authorities declared seven villages as “containment zones.” In nine villages, religious institutions, government buildings, public offices, and educational centers have been shut down. Public transportation is suspended in regions deemed to be at high risk.
In the neighboring states of Tamil Nadu and Karnataka, authorities have ordered tests for visitors from Kerala, with plans for individuals showing signs of influenza to be isolated.
Samples of animal droppings, bat urine, and half-eaten fruit were collected from a village where the first victim of the recent outbreak had lived. The village is near a 300-acre forest where multiple bat species live.
This is the state’s fourth Nipah virus outbreak since 2018. The outbreak in 2018 killed 17 individuals, with more than 230 people subjected to testing. In 2019, the state government placed 300 people under surveillance after a man was found to be infected. In 2021, a third outbreak was recorded, during which a 12-year-old boy died.
“We are the ones who prevented and effectively overcome the Nipah disease. We should not be afraid, but face this situation with caution,” Mr. Vijayan said, suggesting that restrictions may soon be imposed.
Signs and Symptoms, US Risk
According to the U.S. Centers for Disease Control and Prevention (CDC), fruit bats are the “animal reservoir” of the Nipah virus (NiV) in nature. An animal reservoir refers to a species that harbors a virus pathogen and transmits it to humans.“Infection with NiV is associated with encephalitis (swelling of the brain) and can cause mild to severe illness and even death. Outbreaks occur almost annually in parts of Asia, primarily Bangladesh and India,” the agency stated.
Symptoms of the infection can appear within four to 14 days after exposure. The illness initially triggers fever and headache for three to 14 days and could include signs of respiratory illness such as cough, breathing difficulty, and sore throat.
“A phase of brain swelling (encephalitis) may follow, where symptoms can include drowsiness, disorientation, and mental confusion, which can rapidly progress to coma within 24–48 hours,” the CDC stated.
“Death may occur in 40–75 percent of cases. Long-term side effects in survivors of Nipah virus infection have been noted, including persistent convulsions and personality changes.”
At present, there are no licensed treatments available. Treatment is limited to supportive care such as rest, hydration, and dealing with symptoms as they show up.
“There are, however, immunotherapeutic treatments (monoclonal antibody therapies) that are currently under development and evaluation for treatment of NiV infections. One such monoclonal antibody, m102.4, has completed phase 1 clinical trials and has been used on a compassionate use basis,” the CDC stated.
“In addition, the antiviral treatment remdesivir has been effective in nonhuman primates when given as post-exposure prophylaxis, and may be complementary to immunotherapeutic treatments.”
While the only recorded Nipah virus outbreaks have so far been limited to Asia, that doesn’t mean the United States is safe from exposure.
“Years ago, when travel was more restricted, you didn’t see unusual pathogens traveling,” he said.
Nipah virus was first discovered in Malaysia and Singapore in 1999 after an outbreak of the disease in pigs and people. That first outbreak resulted in almost 300 cases, with more than 100 deaths.
The outbreak led to the culling of more than 1 million pigs to control the spread of the infection.
In subsequent outbreaks in India and Bangladesh, the likely source of infection was believed to be the consumption of fruit or fruit products, such as raw date palm juice, that were contaminated with saliva or urine from infected fruit bats.
