India is moving quickly to contain an outbreak of the Nipah virus in the eastern state of West Bengal after five cases, including doctors and nurses who were infected, were confirmed.
Nearly 100 people were asked to quarantine at home, and infected patients were being treated in hospitals in and around the capital Kolkata, according to local media reports, with one patient in critical condition.
Nipah is a deadly virus with no vaccine or cure and is considered a high-risk pathogen by the World Health Organization. Experts say human infections are rare and usually occur when the virus is spread by bats, often through contaminated fruit.
Here’s everything you need to know about this virus:
Nipah virus (NiV) infection: What are the symptoms?
Nipah virus (NiV) infection often begins with non-specific symptoms, making early detection difficult.
According to the US Centers for Disease Control and Prevention (CDC), the incubation period is generally thought to range from four to 21 days, although longer delays between exposure and illness have been reported in rare cases during previous outbreaks.
Patients typically develop a sudden flu-like illness marked by fever, headache, muscle aches and fatigue. In some cases, respiratory symptoms such as cough, shortness of breath or pneumonia also occur, although the timing and severity of these symptoms can vary greatly.
The most serious and defining complication of Nipah infection is inflammation of the brain, known as encephalitis. Neurological symptoms, including confusion, altered consciousness, seizures or coma, usually appear several days to weeks after the initial onset of the disease.
Some patients may also develop meningitis.
File. An officer directs traffic while another clears the Seelong area in the southern state of Johor, 10 May 1999. – Malaysia has extended its pig culling operation to Johor and the eastern state of Kelantan after tests showed positive results for the deadly Nipah virus in 40 pigs (AFP via Getty Images)
How deadly is Nipah virus?
Nipah virus is associated with a high fatality rate, with fatality rates reported between 40 and 75 percent depending on the outbreak and the viral strain involved.
Survivors may experience long-term neurological effects, such as persistent seizures or personality changes, according to the UK Health Safety Agency update.
In rare cases, encephalitis has been reported to recur months or even years after the initial infection, either due to relapse or reactivation of the virus.
How does Nipah virus spread?
The Nipah virus is a zoonotic pathogen that can be transmitted from animals to humans and from person to person, according to the World Health Organization.
The primary natural carriers are fruit bats (Pteropus species); humans can become infected through direct contact with bats or other infected animals, or by consuming food contaminated with bat saliva, urine or faeces.
Human-to-human transmission, particularly through close contact with the bodily fluids of an infected person, has also been reported.
File. Health workers wearing protective gear move a man with Nipah virus symptoms to an isolation ward at a government hospital in Kozhikode in the southern Indian state of Kerala on September 16, 2023 (AFP via Getty Images)
Where was Nipah virus first found?
Nipah virus (NiV) was first identified in 1999 following an outbreak of encephalitis and respiratory disease among pig farmers and others who had close contact with infected pigs in Malaysia and Singapore. The episode led to the recognition of NiV as a serious zoonotic pathogen capable of crossing from animals to humans.
Since then, repeated outbreaks have been recorded in South Asia. Parts of northeastern India and several districts in Bangladesh have reported cases, with Bangladesh experiencing outbreaks almost every year since 2001.
In southern India, the state of Kerala reported its first outbreak of Nipah in 2018, followed by sporadic cases in subsequent years.
Beyond South Asia, infections have also been reported in the Philippines, with investigations suggesting they were caused by the Nipah virus or a closely related Nipah-like strain.
File. A health worker wearing protective gear disposes of biohazard waste from a Nipah virus isolation center at a government hospital in Kozhikode, in the southern Indian state of Kerala, on September 16, 2023 (AFP via Getty Images)
Scientific studies have identified fruit bats as the natural reservoir of the virus. Nipah virus has been isolated from the urine of bats in Malaysia, and antibodies have been found in at least 23 bat species across Asia as well as parts of Africa, including Ghana and Madagascar.
Despite this wide animal reservoir, confirmed human outbreaks have so far been limited to South and Southeast Asia, typically occurring in rural or semi-rural settings where contact between humans, bats and domestic animals is more likely, the WHO says.
“Human-to-human transmission of Nipah virus has also been reported among the family and caregivers of infected patients,” according to the WHO.
Is there any treatment?
There is currently no proven, targeted treatment for Nipah virus (NiV) infection and no approved vaccine to prevent it.
Care for patients remains largely supportive, focusing on managing symptoms and complications as they arise.
The virus is listed by the WHO as a priority pathogen under its Research and Development Blueprint, which identifies epidemic threats that require urgent research.
Reducing the Risk of Nipah Infection:
With no vaccine available, prevention of Nipah virus infection depends on awareness and simple protective measures, global health agencies recommend. Public health advice focuses on reducing contact with the virus, whether from bats, animals, or infected people.
Prevention of bat-to-human transmission: Bats are the main carriers of Nipah. People should avoid consuming raw date palm kernels or fruit that may have been contaminated by bats, WHO guidelines advise.
Boiling fresh date palm juice and thoroughly washing or peeling the fruit can reduce the risk. Any fruit that shows signs of bat bites should be thrown away, advises the health agency.
Prevention of animal-to-human transmission: People handling sick animals, their tissues, or during slaughter should wear gloves and protective clothing. Contact with infected pigs should be minimized, and pig farms in areas with fruit bats should take steps to protect feed and enclosures from bats.
Prevention of human-to-human transmission: Avoid close and unprotected contact with people infected with Nipah. Regular hand washing after caring for or visiting sick individuals is essential to stop the virus from spreading.
Nipah virus in popular culture:
The 2011 movie Contagiondepicting a rapidly spreading global virus, was partly inspired by real-life pathogens such as the Nipah virus, a bat-borne virus first identified in Malaysia in 1999, according to the website of global health non-profit Path.
Nipah causes severe respiratory disease and inflammation of the brain (encephalitis) and can spread from animals to humans, contaminated food, or infected people.
Its high fatality rate, potential for outbreaks, and lack of a vaccine made it a model of how a zoonotic virus could lead to a pandemic, which filmmakers used to shape the realistic global crisis in contagion, Path noted.