Experts in the UK are monitoring an outbreak of Nipah virus in India after two cases of the potentially deadly zoonotic disease were confirmed. The UK Health Security (UKHSA) shared a blog post online with information and advice on preventing infection. It posted on X: “You may have seen Nipah virus mentioned online recently due to an outbreak in India. Understanding symptoms and prevention is important if travelling to an affected area.

“We routinely monitor Nipah virus and no cases have been found in the UK.” Nipah virus was designated a high priority pathogen by the UKHSA last year, meaning it has been flagged as a virus for which new tests, treatments and vaccines are urgently needed. This is due to concerns that a mutation in the virus could one day trigger a pandemic.

Professor Paul Hunter, an expert in medicine at the University of East Anglia said the current risk of person-to-person transmission was low, with each infected person infecting less than one other (a measure known as the R number).

But he added: “Nevertheless, we cannot be complacent as we have seen recently, some virus can mutate to increased infectivity. Also the long incubation period makes detection at borders very difficult.”

Nipah virus typically causes flu-like symptoms or fever, which may develop into pneumonia or other respiratory problems.

In serious cases it can cause inflammation of the brain, known as encephalitis, or meningitis.

Airports in Thailand introduced screening for passengers arriving at major cities from the affected region of India, West Bengal.

Prof Hunter said Nipah virus infection is “usually spread from animals to humans either through direct contact or consumption of contaminated food.

“The primary source of infection is bats and people have been infected from consumption of fruit or fruit products — such as raw date palm juice — contaminated with urine or saliva from infected fruit bats.

“However, the first outbreak was associated with contact with infected pigs. Those pigs probably got infected from bats.

“Person-to-person spread does occur but less commonly. Though, spread from infected patients to their health professionals is a particular concern.”

The death rate for those infection varies between outbreaks. The UKHSA said estimates vary from 40% to 75%.

Prof Hunter said they have been “as low as 9% or as high as 90% of known cases”.

He added: “However, up to about half of infections may not cause any symptoms. So, the mortality rates per infection may be lower than reported.

“The incubation period is usually about one to two weeks but can be longer.”