India is moving quickly to contain an outbreak of the Nipah virus in the eastern state of West Bengal after five cases were confirmed, including doctors and nurses who were infected.
Nearly 100 people were asked to self-quarantine at home and infected patients were 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 treatment and is considered a high-risk pathogen by the World Health Organization. Experts say human infections are rare and usually occur when the virus spills over from 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 most often begins with nonspecific symptoms, making early detection difficult.
According to the US Centers for Disease Control and Prevention (CDC), the incubation period is generally believed to range from four to 21 days, although longer delays between exposure and illness have been reported in rare cases during previous outbreaks.
Patients usually 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. Neurologic 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 official directs traffic as another fogs the Seelong area of southern Johor state, May 10, 1999. – Malaysia has expanded its pig slaughter operation to Johor and eastern Kelantan state 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 mortality rate, with reported mortality levels between 40 and 75%, 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?
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 vectors are fruit bats (Pteropus species); humans can become infected by direct contact with infected bats or other animals, or by eating food contaminated with bat saliva, urine, or feces.
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 into 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 after 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 passing from animals to humans.
Since then, repeated outbreaks have been recorded in South Asia. Parts of northeastern India and several districts of Bangladesh have reported cases, with Bangladesh experiencing outbreaks almost every year since 2001.
In southern India, the state of Kerala reported the 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 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 bat urine in Malaysia, and antibodies have been detected in at least 23 bat species in 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, usually occurring in rural or semi-rural settings where contact between humans, bats and domestic animals is more likely, WHO says.
“Human-to-human transmission of Nipah virus has also been reported among the family and caregivers of infected patients,” according to WHO.
Is there any treatment?
There is currently no proven, targeted treatment for Nipah virus (NiV) infection, and no approved vaccine to prevent it.
Patient care remains largely supportive, focusing on managing symptoms and complications as they occur.
The virus is listed by the WHO as a priority pathogen in its Research and Development Plan, which identifies epidemic threats that require urgent research.
Reducing the risk of Nipah infection:
In the absence of an available vaccine, prevention of Nipah virus infection relies on awareness and simple protective measures, global health agencies advise. Public health advice focuses on reducing contact with the virus, whether from bats, animals or infected people.
Prevention of transmission from bats to humans: Bats are the main carriers of Nipah. People should avoid eating raw date palm sap or fruit that may have been contaminated by bats, the WHO advises.
Boiling fresh date juice and thoroughly washing or peeling the fruit can reduce the risk. Any fruit showing signs of bat bites should be discarded, the health agency recommends.
Prevention of animal-to-human transmission: Gloves and protective clothing should be worn by persons handling sick animals, their tissues or during slaughter. Contact with infected pigs should be minimized, and pig farms in areas with fruit bats should take measures 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 people is essential to stop the spread of the virus.
Nipah virus in popular culture:
The 2011 movie Contagionwhich describes a rapidly spreading global virus, was partly inspired by real-life pathogens such as Nipah virus, a bat-borne virus first identified in Malaysia in 1999, according to the non-profit Path’s website.
Nipah causes severe respiratory disease and inflammation of the brain (encephalitis) and can spread from animals to humans, contaminated food or infected humans.
Its high death rate, potential for outbreaks, and lack of a vaccine made it a model for how a zoonotic virus could trigger a pandemic, which the filmmakers used to model the realistic global crisis in Contagion, The note path.