There is a low risk of the deadly Nipah virus spreading from India, the World Health Organization said on Friday, adding that it did not recommend travel or trade curbs after two infections reported by the South Asian nation.

Hong Kong, Malaysia, Singapore, Thailand and Vietnam are among the Asian locations that tightened airport screening checks this week to guard against such a spread after India confirmed infections.

“The WHO considers the risk of further spread of infection from these two cases is low,” the agency told Reuters in an email on Friday, adding that India had the capacity to contain such outbreaks.

“There is no evidence yet of increased human to human transmission,” it said, adding that it has coordinated with Indian health authorities.

But it did not rule out further exposure to the virus, which circulates in the bat population in parts of India and neighbouring Bangladesh.

Carried by fruit bats and animals such as pigs, the virus can cause fever and brain inflammation. It has a fatality rate ranging from 40% to 75%, with no cure, though vaccines in development are still being tested.

It spreads to humans from infected bats, or fruit they contaminate, but person-to-person transmission is not easy as it typically requires prolonged contact with those infected.

Small outbreaks are not unusual and virologists say the risk to the general population remains low.

The source of infection was not yet fully understood, said the WHO. It classifies Nipah as a priority pathogen because of a lack of licensed vaccines or treatments, a high fatality rate, and a fear it could mutate into a more transmissible variant.

Nipah not new to India 

The two health workers infected in India’s eastern state of West Bengal late in December are being treated in hospital, local authorities have said.

India regularly reports sporadic Nipah infections, particularly in its southern state of Kerala, regarded as one of the world’s highest-risk regions for the virus, linked to dozens of deaths since it first emerged there in 2018.

The outbreak is the seventh documented in India and the third in West Bengal, where outbreaks in 2001 and 2007 were in districts bordering Bangladesh, which reports outbreaks almost annually, the WHO said.