A case of Nipah virus infection has been reported from Kozhikode district in Kerala last week. The 12-year-old boy, who passed away yesterday, had features of encephalitis and myocarditis. The National Centre for Disease Control (NCDC) team has rushed a team the state to monitor the situation.

Kerala has experienced outbreaks of Nipah in 2018 and 2019. In 2018, the outbreak had occurred in  Kozhikode and Malappuram districts of Kerala. At that time, this is the first Nipah virus outbreak in South India and the third in the country, the earlier being in 2001 and 2007, both of which had occurred in West Bengal. Again, in 2019, a new case was detected in Kochi; the patient subsequently recovered. More than 300 people were put under observation, but there were no further infections. Also, no deaths were reported.

Here is a relook at some salient points about Nipah virus infection.

• Nipah virus is a highly pathogenic paramyxovirus.
• Nipah virus infection is a zoonotic disease.
• Nipah virus was first recognized in 1999 during an outbreak among pig farmers in Malaysia. In 2001, it was also reported from Bangladesh. It has been found in other countries like Cambodia, Ghana, Indonesia, Madagascar, the Philippines, and Thailand, including India.
• The fruit bats of the family Pteropodidae, Pteropus genus are the natural reservoir of the virus.
• Transmission: Direct contact via unprotected exposure to secretions from the sick pigs or their contaminated tissues; consumption of fruits or fruit products (such as raw date palm juice) contaminated with urine or saliva from infected fruit bats. Human-to-human transmission has also been reported.
• High risk groups
• Persons exposed to areas inhabited by fruit bats/ articles contaminated by secretions such as, unused wells, caves, fruit orchards, etc
• Persons with direct contact with sick pigs or their contaminated tissues
• Persons in close contact with a Nipah virus affected deceased during burial or cremation rituals
• Health care workers having direct contact with probable or confirmed cases without precautionary measures
• Clinical presentation: Clinically, the presentation of Nipah virus varies from an asymptomatic infection to acute respiratory infection (mild, severe) to fatal encephalitis.
• Symptoms: Non-specific symptoms such as fever, headache, myalgia, vomiting, diarrhea, sore throat and cough, which often preclude diagnosis at the time of presentation. Other symptoms include dizziness, drowsiness, altered consciousness, neurological signs, respiratory distress, seizures. Encephalitis and seizures occur in severe cases, progressing to coma within 24 to 48 hours.
• Incubation period: 4-14 days (maximum 45 days)
• Sequelae: Seizure disorder and personality changes; relapse has been reported or some may develop delayed-onset encephalitis
• Case fatality rate: 40% -75%
• Diagnostic tests: Clinical history, real time polymerase chain reaction (RT-PCR) from bodily fluids and antibody detection via enzyme-linked immunosorbent assay (ELISA). Nipah virus is classified internationally as a biosecurity level (BSL) 4 agent.
• Case definitions (NCDC)
• 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.
• Treatment: No specific treatment, although WHO has identified Nipah as a priority disease for research and development, supportive care with symptomatic infection
• Prevention: Currently, there is no vaccine for Nipah virus, routine and thorough cleaning and disinfection of pig farms, animal health/wildlife surveillance system (One Health approach), education the public about the risk factors and measures to reduce exposure to the infection
• Wash hands with soap and water after coming in contact with a sick person or animal
• Avoid consuming raw date palm sap or toddy
• Eat only fruits that have been washed well
• Avoid eating half eaten fruits from the ground
• Do not enter into abandoned wells
• Handling of dead bodies should be done as per the government advisory
• In case of a suspected outbreak, immediately quarantine the affected animal farm; culling of infected animals with burial or incineration of carcasses under close supervision

References

1. PIB Press release, Ministry of Health & Family Welfare, Sept. 5, 2021
2. Nipah Virus, WHO Fact Sheet, 30 May 2018.
3. Nipah virus outbreak in Kerala, World Health Organization.
4. Nipah virus guidelines. National Center for Disease Control (NCDC).