Nipah virus infection

Nipah virus is a henipavirus that lives in fruit bats of the Pteropodidae family without making them ill. WHO explains that people become infected through direct contact with infected animals, through contaminated food such as raw date palm juice, or from other infected people in close-contact settings. The virus was first recognised during an outbreak in Malaysia and Singapore among pig farmers, and later outbreaks in Bangladesh and India were linked to date palm sap and to spread within families and hospitals.

TravelHealthPro describes spread from fruit bats to humans through contaminated fruits or raw date palm juice, or through infected animals, with person-to-person transmission through close contact with infected people. In date palm regions, bats can feed at collection pots overnight, contaminating the sap with saliva or urine. Caregivers and health workers who look after patients without protective equipment are at particular risk.

• Drinking raw date palm sap or eating fruit with bat bite marks.

• Handling sick animals, particularly in outbreak settings.

• Close, unprotected care of an infected person.

TravelHealthPro notes infections range from asymptomatic to mild respiratory illness, and some people develop fatal brain inflammation. WHO describes fever and symptoms affecting the brain, such as headache and confusion, and/or the lungs. Early symptoms resemble many other infections: fever, headache, muscle pain, vomiting and sore throat, followed in severe cases by drowsiness, disorientation, seizures and coma over a day or two. Some survivors have long-term neurological problems, and rare relapses have been reported months or years later.

WHO estimates that the case fatality rate is between 40 and 75 per cent, with severe neurological involvement particularly associated with poor outcomes. The wide range reflects differences in the virus strain and in the quality of intensive care available.

• Fever, headache and muscle pain.

• Cough, sore throat and breathing difficulty.

• Drowsiness, confusion, seizures and reduced consciousness.

Diagnosis requires specialist laboratory testing, so in the UK a returning traveller with compatible symptoms and a relevant exposure would be assessed urgently through infectious disease services and UKHSA. Malaria and other common causes are excluded first. WHO states that early diagnosis promotes early supportive care, which includes oxygen therapy, organ support and careful monitoring. TravelHealthPro notes there are no specific antivirals.

WHO reports several vaccine candidates under development but none yet approved, so prevention rests on avoiding exposure.

Both WHO and TravelHealthPro advise boiling freshly collected date palm juice, washing and peeling fruit, and discarding fruit with bat bite marks. Avoid contact with sick animals and use protective equipment when handling them, keep a distance from infected people and wash hands regularly. Health workers should use contact and droplet precautions, including a well-fitting medical mask, eye protection and a fluid-resistant gown, according to WHO.

TravelHealthPro describes the risk as very low for tourists who follow standard precautions in endemic areas. Check TravelHealthPro country pages before travel to Bangladesh or India in the date palm sap season, when most cases occur.

If you develop fever, headache, confusion or breathing symptoms within about three weeks of returning from an area with Nipah outbreaks, contact NHS 111 or the emergency department by phone and mention your travel and any contact with sick animals, raw date palm juice or ill people. Call 999 for severe breathing difficulty, seizures or reduced consciousness.