Nipah virus (NiV) : Key facts, Transmission & Prevention
Nipah virus (NiV) is an emerging zoonotic virus (a virus transmitted to humans from animals). In infected people, Nipah virus causes a range of illnesses from asymptomatic (subclinical) infection to acute respiratory illness and fatal encephalitis. NiV can also cause severe disease in animals such as pigs, resulting in significant economic losses for farmers.
Nipah virus is closely related to Hendra virus. Both are members of the genus Henipavirus, a new class of virus in the Paramyxoviridae family.
Although Nipah virus has caused only a few outbreaks, it infects a wide range of animals and causes severe disease and death in people, making it a public health concern.
NiV is a zoonotic virus (a virus transmitted to humans from animals). During the initial outbreaks in Malaysia and Singapore, most human infections resulted from direct contact with sick pigs or their contaminated tissues. Transmission is thought to have occurred via respiratory droplets, contact with throat or nasal secretions from the pigs, or contact with the tissue of a sick animal.
In the Bangladesh and India outbreaks, consumption of fruits or fruit products (e.g. raw date palm juice) contaminated with urine or saliva from infected fruit bats was the most likely source of infection.
Limited human to human transmission of NiV has also been reported among family and care givers of infected NiV patients. During the later outbreaks in Bangladesh and India, Nipah virus spread directly from human-to-human through close contact with people’s secretions and excretions. In Siliguri, India, transmission of the virus was also reported within a health-care setting (nosocomial), where 75% of cases occurred among hospital staff or visitors. From 2001 to 2008, around half of reported cases in Bangladesh were due to human-to-human transmission through providing care to infected patients.
Controlling Nipah virus in domestic animals
Currently, there are no vaccines available against Nipah virus. Routine and thorough cleaning and disinfection of pig farms (with appropriate detergents) may be effective in preventing infection.
If an outbreak is suspected, the animal premises should be quarantined immediately. Culling of infected animals – with close supervision of burial or incineration of carcasses – may be necessary to reduce the risk of transmission to people. Restricting or banning the movement of animals from infected farms to other areas can reduce the spread of the disease.
As Nipah virus outbreaks in domestic animals have preceded human cases, establishing an animal health surveillance system, using a One Health approach, to detect new cases is essential in providing early warning for veterinary and human public health authorities.
Reducing the risk of infection in people
In the absence of a licensed vaccine, the only way to reduce infection in people is by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to and decrease infection from NiV.
Public health educational messages should focus on the following:
- Reducing the risk of bat-to-human transmission: Efforts to prevent transmission should first focus on decreasing bat access to date palm sap and to other fresh food products. Keeping bats away from sap collection sites with protective coverings (e.g., bamboo sap skirts) may be helpful.Freshly collected date palm juice should be boiled and fruits should be thoroughly washed and peeled before consumption.
- Reducing the risk of animal-to-human transmission: Gloves and other protective clothing should be worn while handling sick animals or their tissues, and during slaughtering and culling procedures. As much as possible, people should avoid being in contact with infected pigs.
- Reducing the risk of human-to-human transmission: Close unprotected physical contact with Nipah virus-infected people should be avoided. Regular hand washing should be carried out after caring for or visiting sick people.
Controlling infection in health-care settings
- Health-care workers caring for patients with suspected or confirmed NiV infection, or handling specimens from them, should implement standard infection control precautions for all patients at all times
- As human-to-human transmission in particular nosocomial transmission have been reported, contact and droplet precautions should be used in addition to standard precautions.
- Samples taken from people and animals with suspected NiV infection should be handled by trained staff working in suitably equipped laboratories.
- Nipah virus is an RNA virus that is part of the Paramyxovidae family that was first identified as a zoonotic pathogen after an outbreak involving severe respiratory illness in pigs and encephalitic disease in humans in Malaysia and Singapore in 1998 and 1999.
- Nipah virus can cause a range of mild to severe disease in domestic animals such as pigs.
- Nipah virus infection in humans causes a range of clinical presentations, from asymptomatic infection (subclinical) to acute respiratory infection and fatal encephalitis.
- Nipah virus can be transmitted to humans from animals (bats, pigs), and can also be transmitted directly from human-to-human.
- Fruit bats of the Pteropodidae family are the natural host of Nipah virus.
- There is no treatment or vaccine available for either people or animals. The primary treatment for humans is supportive care.
- Nipah virus is on the WHO list of Blueprint priority diseases