Wuhan institute says Nipah virus has 40 to 70% mortality rate, but human transmission rare according to experts

Health authorities in some parts of Asia are on alert following the re-emergence of the Nipah virus in India.

This comes after two Nipah virus cases were reported in India's eastern state of West Bengal, according to Indian media reports.

India’s health ministry said the two cases, which were confirmed in December, involved healthcare workers, BBC reported.

A total of 196 people identified as close contacts have since been traced and tested, all of whom returned negative results.

There are currently no approved vaccines or treatments for the virus, and fatality rates in previous outbreaks have ranged from 40 to 75 per cent since its first known outbreak in Malaysia in 1998, according to the Wuhan virology institute.

Similary, Singapore's National Centre for Infectious Diseases also gave the same number on their page on Nipah.

" It is a highly fatal illness, with a case fatality ratio (CFR) estimated between 40 to 75% in past outbreaks depending on local capabilities for epidemiological surveillance and clinical management (CFR ~ 40% for outbreaks in Malaysia and Singapore; CFR >70% for outbreaks in Bangladesh)."

What is the Nipah virus?

The Nipah virus is a zoonotic disease, which means that it can be transmitted from animals to humans, BBC reported.

Nipah is also classified by the World Health Organisation (WHO) as a priority pathogen due to its epidemic potential.

There is no approved vaccine or specific treatment, and even small clusters of infections are treated with caution.

The incubation period typically ranges from four to 14 days.

Infected individuals may experience a wide range of symptoms, while some may remain asymptomatic.

Early symptoms include fever, headache, muscle pain, vomiting and sore throat.

In certain cases, these may progress to drowsiness, altered consciousness and pneumonia.

Severe infections can lead to encephalitis, a potentially fatal inflammation of the brain.

Former president of the Asia-Pacific Society of Clinical Microbiology and Infection, Paul Tambyah, told The Straits Times that the Nipah virus is not very contagious.

He further added that direct human transmission is rare and no instances of Nipah spreading through "casual contact" have been documented.

He also pointed to the official Indian Health Ministry statement that there are only two confirmed cases in this current outbreak, despite screening over a hundred contacts of the index case.

Health authorities

According to Global Times, Wang Xinyu, the deputy director of the infectious diseases department at Huashan Hospital affiliated with Fudan University, wrote on the hospital’s WeChat public account on Jan. 26 that data from WHO indicated that while the situation has not escalated into a large-scale outbreak, smaller clusters with high fatality rates continue to emerge in certain parts of India.

These outbreaks show signs of cross-regional spread and hospital-based transmission.

Wang also noted that the most significant characteristic of the Nipah virus is its high mortality rate, which ranges from 40 to 75 per cent.

Wang added that recent cases in India indicate the virus may be appearing outside its typical seasonal pattern, which is usually linked to the winter date harvest season.

"This suggests the virus may be adapting to new environments or exploring new routes of transmission," he wrote.

Thailand's Ministry of Public Health has begun screening travellers arriving at Suvarnabhumi and Don Mueang airports, with a focus on travellers from West Bengal.

Those who develop symptoms such as fever, headache, muscle aches, sore throat, cough, difficulty breathing, drowsiness, confusion or seizures are advised to seek medical attention immediately, particularly if they have had contact with bats, sick animals or infected individuals within 21 days prior to arrival.

According to BBC, Nepal has also stepped up screening measures for arrivals at Kathmandu's airport, as well as at land border crossings with India.

In Taiwan, health authorities have proposed the listing of the Nipah virus as a "Category 5 disease". Under the island's disease classification system, Category 5 covers emerging or rare infections that pose significant public health risks and require immediate reporting and special control measures.

Advice to travellers

According to Singapore's Communicable Diseases Agency (CDA), the Nipah virus was first identified in an outbreak in Malaysia and Singapore between 1998 and 1999, primarily among people with close contact with pigs.

The majority of cases during that outbreak involved encephalitis or neurological symptoms, with no evidence of human-to-human transmission.

Travellers heading to areas affected by the virus are advised to remain vigilant and observe the following health precautions when overseas:

• Observe good personal hygiene including frequent hand washing with soap and water
• Avoid exposure to pigs and bats
• Avoid areas where bats are known to roost
• Avoid eating or drinking products that could be contaminated by bats, such as raw date palm sap, raw fruit that is found on the ground
• Avoid contact with blood or body fluids of any person known to be infected with Nipah virus

Travellers who have had high-risk exposures, such as contact with bat excretions in Nipah virus-affected areas, should seek medical attention immediately.

Those who feel unwell during or after travel to affected areas are encouraged to wear a mask and see a doctor promptly. They should also inform their doctor of their recent travel history and any potential high-risk exposures.

Top photos via Reuters