India Nipah virus disease – On 4 September 2021, the Kerala State Health department reported an isolated case of Nipah virus disease in Kozhikode district, Kerala state, India. Nipah has a relatively high case fatality ratio, and is an emerging zoonotic disease of public health importance in the South East Asia and Western Pacific WHO Regions. This is the fifth outbreak of the disease in India.
On 29 August, a 12 year-old boy developed low grade fever, and the family sought care at a local health care facility. On 31 August, he was transferred to several hospitals as his condition deteriorated. On 1 September, the patient’s condition continued to deteriorate, and the family requested his transfer to another hospital in Kozhikode.
On 3 September, plasma, serum and cerebrospinal fluid samples were sent to the National Institute of Virology in Pune, India. On 4 September, the presence of Nipah virus in the plasma, cerebrospinal fluid and serum samples was confirmed by real-time polymerase chain reaction (RT-PCR) and IgM antibodies was confirmed in the plasma sample by ELISA serology test. On 5 September, the patient died and a safe burial and cremation were performed the same day in Kozhikode.
As of 6 September, epidemiological investigations identified contacts, including health care workers and close family members, who were placed under quarantine.
Public health response
The following public health responses were implemented:
1、The state government held a meeting of senior health officials to plan and implement response measures;
2、A district core committee was formed, and a district Nipah virus disease action plan was released for all stakeholders;
3、A multi-disciplinary central team from the National Centre for Disease Control was sent to Kerala state to provide technical support. Immediate public health measures were applied, including active case finding in the family, hospitals, village and areas with similar topography especially in Malappuram district, located in the southeast of Kozhikode district;
4、Risk communication messages to the public about the transmission of Nipah virus disease and prevention measures were provided;
5、State authorities issued an alert to Mysuru, Mangaluru, Chamarajanagar and Kodagu districts in Karnataka state, which border Kerala state.
WHO risk assessment
Nipah virus disease is an emerging zoonotic disease of public health importance in the WHO South East Asia and Western Pacific Regions, where Pteropus fruit bats, the natural host of the virus, are widespread. It was first identified during an outbreak in Malaysia in 1998, and all subsequent outbreaks have occurred in parts of Asia (India, Bangladesh, Malaysia and Singapore).
Transmission can occur from direct contact with infected animals, consuming contaminated food products or through close contact with an infected person. Previous outbreaks had a seasonal pattern with occurrence during winter and spring, associated with several factors such as the breeding season of the bats, increased virus shedding by bats and fruit harvesting season. The case fatality ratio ranges from 40 to 100%.
In India, the first Nipah virus disease outbreak was reported in Siliguri town in 2001, followed by a second outbreak in Nadia district in 2007, both in West Bengal state. In 2018, an outbreak was reported in Kozhikode district, and in 2019, another outbreak in Kochi district, both in Kerala state. Bats from the Pteropus spp. were the probable source of the 2018 outbreak in Kerala state.
The current isolated case was reported in a rural area in Kerala state where an outbreak was previously reported in 2018. India has experienced and contained Nipah virus disease outbreaks in the past and has demonstrated the capacity to carry out outbreak control activities, including case identification, laboratory testing, case management, contact tracing and risk communication. This event is an isolated case and the risk is low at national level and low at the regional level.
While there are no licensed vaccines or treatments available, experimental monoclonal antibodies have been developed to treat Nipah virus disease under compassionate use. Case management should focus on the delivery of supportive care measures to patients. Intensive supportive care is recommended for patients with severe respiratory and neurologic complications.
There is evidence of Nipah virus disease among several species of domestic animals including dogs, cats, goats, sheep and horses. Nipah virus disease can be prevented by avoiding exposure to bats and sick animals in endemic areas, and avoiding consumption of fruits partially eaten by bats, and avoiding drinking raw date palm sap/toddy/juice. The risk of infection and international transmission via fruit or fruit products, such as raw date palm sap/toddy/juice contaminated with urine or saliva from infected fruit bats can be prevented by washing them thoroughly and peeling them before consumption.
In health care settings, staff should consistently implement standard infection prevention and control measures when caring for patients to prevent nosocomial infections. Health care workers caring for a patient suspected to have Nipah virus disease should immediately contact local and national experts for guidance and to arrange for laboratory testing.
Safe and dignified burial is required for all confirmed and suspected cases of Nipah virus disease.WHO advises against the application of any travel or trade restrictions on India based on the current information related to this event.