The Nipah virus (NiV) is a rare but serious infectious disease that has caused periodic outbreaks in parts of Asia – Why, Why and How?
Although the risk of the Nipah virus to most travellers is low, understanding how the virus spreads and how to reduce exposure is important, especially if you are visiting regions where it circulates. Importantly, no cases of Nipah virus have ever been detected in the UK.
What Is the Nipah Virus?
Nipah virus is a zoonotic virus, meaning it can spread from animals to humans. It can also be transmitted through contaminated food and, in some circumstances, from person to person.
The virus was first identified in 1999 during an outbreak among pig farmers in Malaysia and Singapore. Since then, further outbreaks have been reported in South and Southeast Asia.
Fruit bats, particularly flying foxes of the Pteropus genus, are the natural hosts of the Nipah virus. These bats can carry the virus without appearing ill. Nipah virus can also infect other animals, including pigs, dogs, cats, goats, horses and sheep, sometimes acting as a bridge between bats and humans.
Understanding the symptoms
The incubation period for Nipah virus is usually 4-21 days, although longer periods have been reported.
Early symptoms are often non-specific and may resemble a flu-like illness, with fever, headache, muscle pain and fatigue. Some people also develop respiratory symptoms such as cough, shortness of breath or pneumonia.
The most severe complication is encephalitis, an inflammation of the brain, or meningitis. This can develop several days to weeks after the initial illness and is considered the hallmark of Nipah infection.
The disease has a high fatality rate, with an estimated 40 to 75% of infected people dying. Survivors may experience long-term neurological problems, including seizures, changes in behaviour or personality, and, in rare cases, the virus can reactivate months or years later.
Where is the Nipah virus found?
Human outbreaks of the Nipah virus have been identified only in South and South-East Asia, usually in rural or semi-rural areas. Countries that have previously reported outbreaks include Bangladesh, where cases have occurred almost every year since 2001; India; Malaysia; Singapore; and the Philippines.
Although antibodies to Nipah virus have been found in bat populations across parts of Asia, Ghana and Madagascar, human outbreaks have not occurred outside South and South-East Asia.
How does the Nipah virus spread?
People can become infected through direct contact with infected animals or their bodily fluids. However, many infections are linked to eating or drinking food contaminated with fruit bat droppings. This includes fruit that has been partially eaten by bats and raw or partially fermented date palm sap, which can be contaminated by bat saliva, urine or droppings.
Person-to-person transmission has been documented, particularly among close contacts such as family members or caregivers. Transmission is more likely when infected individuals have respiratory symptoms and when exposure occurs through bodily fluids.
Is there a treatment or vaccine?
There is currently no proven specific treatment for Nipah virus infection, nor is there a licensed vaccine. Care for infected patients focuses on intensive supportive treatment, particularly for severe respiratory or neurological illness.
Several experimental therapies, including antivirals and monoclonal antibodies, are under development. Nipah virus is recognised internationally as a priority pathogen requiring urgent research.
The risk to most travellers is very low. Anyone who develops symptoms while abroad in an affected area should seek medical advice immediately. If symptoms appear after returning to the UK, it is important to inform a healthcare provider about recent travel history.
Why is this important now?
It’s important to understand the Nipah Virus at this time, as two cases have been confirmed in India, and it is considered a high-risk pathogen by the World Health Organisation.
