An outbreak of Nipah virus disease has been reported from Kerala. This article compiles essential information about Nipah virus disease.

Background Information:

Nipah virus (NiV) is a zoonotic virus (it is transmitted from animals to humans) and can also be transmitted through contaminated food or directly between people. In infected people, it causes a range of illnesses from asymptomatic (subclinical) infection to acute respiratory illness and fatal encephalitis.

It is an emerging zoonotic disease which was first recognized in a large outbreak of 276 reported cases in Malaysia and Singapore from September 1998 to May 1999.

In India, during 2001 and 2007 two outbreaks in humans were reported from areas in West Bengal adjoining Bangladesh. In 2018 an outbreak in humans was reported from north Kerala.

The current outbreak in Kerala is classified as a ‘local occurrence’ by the Ministry of Health and Family Welfare (MoHFW) and is not a major outbreak.

Key Messages:

Epidemiology

Agent: NiV is a member of the family Paramyxoviridae, genus Henipavirus.

Natural Reservoir: The animal host reservoir for NiV is the fruit bat (genus Pteropus), also known as the flying fox.
Presumably, pigs may become infected after consumption of partially bat eaten fruits
that are dropped in pigsties.

Incubation Period: Ranges from 4 to 45 days, with symptoms typically appearing between 4 to 14 days following exposure to the virus.

Transmission:

Nipah virus (NiV) can spread to people from:

• Direct contact with infected animals, such as bats or pigs, or their body fluids (such as blood, urine or saliva)
• Consuming food products that have been contaminated by body fluids of infected animals (such as palm sap or fruit contaminated by an infected bat)
• Close contact with a person infected with NiV or their body fluids (including nasal or respiratory droplets, urine, or blood)

In the first known NiV outbreak, people were probably infected through close contact with infected pigs. The NiV strain identified in that outbreak appeared to have been transmitted initially from bats to pigs, with subsequent spread within pig populations. Then people who worked closely with infected pigs began falling ill. No person-to-person transmission was reported in that outbreak.

However, person-to-person spread of NiV is regularly reported in Bangladesh and India. This is most commonly seen in the families and caregivers of NiV-infected patients, and in healthcare settings. Transmission also occurs from exposure to food products that have been contaminated by infected animals, including consumption of raw date palm sap or fruit that has been contaminated with saliva or urine from infected bats. Some cases of NiV infection have also been reported among people who climb trees where bats often roost.

Clinical Features:

Infection with Nipah virus (NiV) can cause mild to severe disease, including swelling of the brain (encephalitis) and potentially death.

Symptoms typically appear in 4-14 days following exposure to the virus. The illness initially presents as 3-14 days of fever and headache, and often includes signs of respiratory illness, such as cough, sore throat, and difficulty breathing. A phase of brain swelling (encephalitis) may follow, where symptoms can include drowsiness, disorientation, and mental confusion, which can rapidly progress to coma within 24-48 hours.

Symptoms may initially include one or several of the following:

• Fever
• Headache
• Cough
• Sore throat
• Difficulty breathing
• Vomiting

Severe symptoms may follow, such as:

• Disorientation, drowsiness, or confusion
• Seizures
• Coma
• Brain swelling (encephalitis)

Death may occur in 40-75% of cases (this varies from outbreak to outbreak). Long-term side effects in survivors of Nipah virus infection have been noted, including persistent convulsions and personality changes.

Diagnosis:

Suspect Nipah Case
Person from a community affected by a Nipah virus (NiV) disease outbreak who has:

• Fever with new onset of altered mental status or seizure and/or
• Fever with headache and/or
• Fever with Cough or shortness of breath

Probable Nipah Case
Suspect case-patient/s who resided in the same village/ward, where suspect/confirmed
case of Nipah were living during the outbreak period and who died before complete
diagnostic specimens could be collected.
OR
Suspect case-patients who came in direct contact with confirmed case-patients in a
hospital setting during the outbreak period and who died before complete diagnostic
specimens could be collected.

Confirmed Nipah Case
Suspected case who has laboratory confirmation of Nipah virus infection either by:

• Nipah virus RNA identified by PCR from respiratory secretions, urine, or cerebrospinal fluid.
• Isolation of Nipah virus from respiratory secretions, urine or cerebrospinal fluid.

Differential Diagnoses:

• Dengue
• Japanese Encephalitis
• Cerebral malaria
• Scrub typhus
• Bacterial meningitis
• Herpes simplex encephalitis
• other viral encephalitis

Treatment:

Currently there is no known treatment or vaccine available for either people or animals. The drug ribavirin was used to treat a small number of patients in the initial Malaysian NiV outbreak, but its efficacy in people is unclear.

Intensive supportive care with treatment of symptoms is the main approach to to treat severe respiratory and neurologic complications.

Prevention:

In areas where Nipah virus (NiV) outbreaks have occurred (Bangladesh, Malaysia, India, and Singapore), people should:

• Practice handwashing regularly with soap and water
• Avoid contact with sick bats or pigs
• Avoid areas where bats are known to roost
• Avoid entering into abandoned wells
• Avoid consumption of raw date palm sap
• Avoid consumption of fruits that may be contaminated by bats
• Avoid contact with the blood or body fluids of any person known to be infected with NiV
• Handling of dead bodies should be done in accordance with the government advisory

Because NiV can be spread from person-to-person, standard infection control practices and proper barrier nursing techniques are important in preventing hospital-acquired infections (nosocomial transmission) in settings where a patient has confirmed or suspected NiV infection.

For Health care personnel:

• Wash hands thoroughly with soap and water for 20 seconds after contact with a sick patient.
• While handling Nipah cases (suspected/ confirmed), standard precautions for infection control should be practiced.
• For aerosol generating procedures, PPE such as individual gowns (impermeable), gloves, masks and goggles or face shields and shoe cover and the procedure should be performed in airborne isolation room.
• Dedicated medical equipment should be used (preferably disposable whenever possible).
• All non-dedicated, non-disposable medical equipment used for patient care should be cleaned and disinfected as per manufacturer’s instructions and hospital policies.
• Use of injections and sharps should be limited.
• Safe waste disposal for potentially infected material including used PPE, linen, clothing of patient according standard biomedical waste management guidelines.
• Admit all suspected cases of Nipah to the isolation ward/ facility in the hospital. Once the case is suspected of NIPAH, attendants should not be permitted in the ward.
• Segregate all suspected cases of Nipah patients from all patients in the isolation ward/ facility.
• Avoid unnecessary contact with suspected Nipah cases or use barrier nursing.
• Any spillage of body fluids in the OP/Ward should be managed as per Infection control guidelines.
• Mortuary staff should wear PPE while handling corpse of Nipah. Air sealed bag should be used for transportation of the dead body.

Useful Links:

Link to WHO fact sheet on Nipah virus:

https://www.who.int/news-room/fact-sheets/detail/nipah-virus

Link to US CDC information page on Nipah virus infection:

https://www.cdc.gov/vhf/nipah/index.html

Link to India’s Ministry of Health and Family Welfare page containing guidelines on Nipah Virus:

https://www.ncdc.gov.in/index4.php?lang=1&level=0&linkid=113&lid=228