Nipah virus infection

Overview

Nipah virus infection is a zoonotic disease caused by the Nipah virus (NiV), a zoonotic virus which can transmit from animals to humans. It can also be transmitted through contaminated food or directly between humans.

NiV was first identified in an outbreak among people with close contact with pig in Malaysia and Singapore in 1998-1999. A high incidence of cases during this outbreak presented with encephalitis or had neurological symptoms, with no occurrence of human-to-human transmission. In subsequent outbreaks in Bangladesh and India, a higher incidence of respiratory involvement was reported with limited human-to-human transmission. NiV poses a recurring risk across parts of South Asia, as its animal reservoir, fruit bats, is widely distributed across the region.

Pathogen(s)

Nipah Virus (Henipavirus genus, Paramyxovirus family).

Transmission

Animal-to-human transmission may occur through:

• Direct contact with infected animals, such as bats and pigs, or their bodily fluids or excretions

• Consumption of raw date palm sap or fruits contaminated by saliva or urine of infected bats

• Limited human-to-human transmission of NiV among family, caregivers, community contacts, and healthcare providers of infected NiV patients through close contact with their secretions and excretions has been documented

Incubation period: Usually 4 to 14 days, but can be as long as 45 days.

Infectious period: Unknown. It likely begins during the incubation period and continues until the patient stops shedding the virus.

Clinical features

NiV infections range from asymptomatic infection to mild to severe disease, and fatal encephalitis. The initial clinical manifestations of NiV infection are non-specific and are similar to other diseases such as viral encephalitis, bacterial meningoencephalitis and pneumonia.

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). Patients with NiV infection may present with the following symptoms:

• Acute encephalitis picture characterised by initial symptoms of fever, headache, myalgia, vomiting, sore throat, followed by dizziness, drowsiness, altered consciousness, seizures in severe cases, which may progress to coma within 24 to 48 hours

• Atypical pneumonia, and acute respiratory distress

• Relapse encephalitis and late-onset encephalitis in those with initial non-encephalitic or asymptomatic diseases reported

Risk factors

• Travel history to NiV affected countries or regions with ongoing NiV outbreak

• Exposure to bats or bat-contaminated food or pigs

• Exposure to a confirmed NiV case

• Consumption of sap or other products from palm trees

Diagnosis

Diagnosis in acute infection is primarily by detection of NiV by (polymerase chain reaction) PCR in blood, CSF samples and throat swab in UTM.

Treatment and management

There are no specific licensed antivirals for treatment of NiV infection. While ribavirin has been used to treat NiV infection, evidence is limited and its efficacy remains uncertain. Treatment is mainly supportive, including management of symptoms and complications such as severe respiratory failure and neurological complications (e.g., seizures). Clinical care is guided by Infectious Diseases specialists, with involvement of multidisciplinary team as per clinical needs.

Precaution, prevention, and control

Advice for Travellers

Travellers to NiV affected areas are encouraged to maintain vigilance and adopt the following health precautions when overseas:

• Observe good personal hygiene including frequent hand washing with soap and water or with hand sanitisers with at least 60% alcohol content

• Do not eat or drink products that could be contaminated by bats, such as raw date palm sap, fruit found on the ground

• Avoid contact with pigs and bats and bat roosting places

• Avoid contact with blood or bodily fluids of any person known to be infected with NiV or persons who are unwell

• Eat food that is fully cooked and fruits that can be washed and peeled

Individuals who feel unwell during or after their trip should seek medical attention promptly. They should inform their doctor of their recent travel to NiV affected areas and any potential exposures to raw date palm sap, bats or unwell persons.

There is no licensed vaccine for NiV at present.

Infection Prevention and Control

• Patients who are under investigation or confirmed to have NiV infection should ideally be isolated in an airborne infection isolation room (AIIR) and be placed on strict contact, droplet and airborne precautions. Healthcare staff directly involved in patient care should don PPE comprising gown, gloves, N95 mask and eye protection (face shield/ eye goggles) when attending to these patients. Risk to healthcare staff can be mitigated with good infection prevention and control practices. Visitors should not be allowed.

• All waste generated during the care of NiV suspect and confirmed patients should be handled as biohazard waste, according to institutional policy.

• Linen and laundry from suspects and confirmed cases should be managed as infectious linen and laundry. Institutions may consider the use of disposable linen.

• Rooms occupied by suspect or confirmed cases of NiV should be terminally cleaned with bleach-based disinfectants after discharge. Enhancement of terminal cleaning with either UV-C disinfection system or hydrogen peroxide vaporisation is recommended.

• On the management of deceased bodies of suspect or confirmed cases of NiV, the handling of the body should be kept to a minimum. The ward/hospital staff should ensure the following:

  • All orifices must be plugged in with 10,000 ppm sodium hypochlorite.

  • The body is double-bagged in sealed and leak-proof heavy-duty plastic cadaveric body bags, before the body is taken out of the isolation room.

  • The surface of each body bag is wiped down with a suitable disinfectant (e.g. bleach), sealed and affixed with a ‘biohazard’ label.

  • The body should not be sprayed, washed or embalmed.

Notification

Who should notify:

• Medical practitioners

• Laboratories

When to notify:

• On clinical suspicion or laboratory confirmation

How to notify:

• Nipah virus infection is a notifiable disease under the Infectious Diseases Act (IDA)

• Report all suspected and confirmed cases immediately to CDA's Surveillance Duty Officer

• Submit case details thereafter via the Communicable Diseases Live & Enhanced Surveillance (CDLENS) system

• Please refer to the Infectious Disease Notification for more information.

Notification timeline:

• Immediately. No later than 24 hours from the time of diagnosis.