Nipah virus infection - WHO event update
Nipah virus infection -WHO event update (Sep 28 2023)
Nipah virus (NiV) infection is an emerging bat-borne zoonotic disease transmitted to humans through infected animals (such as bats and pigs) or food contaminated with saliva, urine, and excreta of infected animals. It can also be transmitted directly from person to person through close contact with an infected person (although this represents a less common transmission route).
NiV infection in humans causes a range of clinical presentations, from asymptomatic infection (subclinical) to acute respiratory infection and fatal encephalitis. The overall global case fatality rate is estimated at 40% to 75% depending on the specific NiV strain and capabilities for epidemiological surveillance and clinical management. There are currently no effective therapeutic or vaccine is available.
The current outbreak reemerged in Kerala state this year, and as of 22 September 2023, six confirmed NiV-infected cases have been reported including two deaths with case fatality ratio (CFR) of 33%.
Outbreaks have been reported since 1998 in Malaysia, Bangladesh, India, the Philippines, and Singapore. This is the third NiV outbreak in Kozhikode district, Kerala, and the fourth outbreak in Kerala since 2018. As in the previous outbreak in 2018, the current outbreak started with the first case (primary case) and subsequent clustering of cases in family contacts and likely nosocomial transmission in hospitals. The previous outbreaks in Kerala have occurred between May and September.
International disease spread
The risk of the international spread of the virus is low from the current outbreak. All cases have been reported within the Kozhikode district of Kerala and as per available information from the affected cases, there is no travel history outside the district. Containment zones have been declared in nine villages in Kozhikode district and movement of people is restricted.
Current Outbreak in Kerala
Between 12 – 15 September 2023, a total of six laboratory-confirmed cases of NiV infection, including two deaths were reported in Kozhikode district, Kerala state, India. The case fatality ratio (CFR) in the current outbreak is 33%.
As of 27 September, a total of 1,288 contacts were traced including high-risk contacts and healthcare workers (HCW) and all of them were under quarantine. Since 12 September 2023, 387 samples were tested out of which only six cases were positive and the remaining were negative. Since 15 September no positive cases have been identified and as of 27 September, 865 contacts remain in quarantine.
According to the National Institute of Virology (NIV), Pune, the virus found in Kerala has been identified as the Indian Genotype or I-Genotype. It is similar to the strain found in Bangladesh.
Public Health Response
The following public health response measures have been undertaken by the Department of Health and Family Welfare, State Government of Kerala with support from the Ministry of Health and Family Welfare, Government of India, and its institutions Indian Council of Medical Research (ICMR), National Institute of Virology (NIV), Pune, and National Institute of Epidemiology, Chennai.
Coordination: Multiple Central multi-disciplinary teams have been mobilized by the Department of Health & Family Welfare, Department of Health Research as well as Department of Animal Husbandry to aid the State and District administration in containment and mitigation measures.
A total of 19 core committees were created and tasked with various response measures including surveillance, sample testing, contact tracing, patient transportation, case management, logistics and supplies, training and capacity building, risk communication and community engagement, psychosocial support and animal husbandry. A control room with a call centre has been activated in the district to coordinate the response activities.
Surveillance and contact tracing: As part of community-based surveillance activities, active house-to-house surveillance was carried out by the District health authorities in the containment zones declared. A total of 53,708 houses have been surveyed as of 27 September 2023.
As of 27 September, a total of 1 288 contacts were traced including high-risk contacts and all the HCWs who handled the patient/samples were under quarantine. All high-risk contacts were tested.
Containment zones were declared in nine villages in Kozhikode district with movement restrictions, closure of non-essential activities including schools and colleges, social distancing and mandatory mask wearing in public spaces. The government has restricted major public events in Kozhikode district until 1 October 2023.
Alerts have been issued to neighboring districts and states for enhanced surveillance.
Laboratory testing: Laboratory testing of suspect cases as well as environmental and animal samples is being conducted at the Regional Viral Research and Diagnostic Laboratory (VRDL) network lab at Government Medical College (GMC), Kozhikode; ICMR’s Mobile BSL-3 lab; Field unit of NIV at Alappuzha as well as NIV, Pune. No environmental/ animal samples (including bats) have tested positive for Nipah virus, so far.
Health facility preparedness: Emergency departments have been equipped to handle any suspected cases and respond to emergencies. Isolation rooms and intensive care units (ICU) are being kept ready to treat suspects, if required. The state has earmarked isolation rooms, ICU beds, and ventilators to mount surge capacity (if needed).
Suspect/confirmed cases are being managed at identified health facilities. For patient transport, dedicated ambulances have been mobilized.
Following the first NiV infection outbreak in Kerala in 2018, the State Government and the Government of India had previously developed various guidelines including surveillance, case management, infection prevention and control, laboratory sample collection and transport, advisory for healthcare workers and the general public etc. which were put in use during this outbreak.
Infection prevention and control (IPC): The State Government has initiated training of healthcare workers on infection prevention and control. Adequate stocks of Personal Protective Equipment (PPEs) have been made available to healthcare workers. (IPC) practices are being strictly adhered to and audited.
Animal Sector: Samples of bats, animal droppings, and half-eaten fruit were collected on 15 September from Maruthonkara, the village where the primary case lived, in a 300-acre (121-hectare) forest which is home to several bat species.
The State Health Department and the Union Ministry of Health & Family Welfare continue to monitor the situation.
WHO Risk Assessment
This is the sixth outbreak in India since 2001 when the first outbreak was reported in Siliguri town, West Bengal (66 cases, CFR: 68%). Subsequently, five outbreaks have been reported- Nadia district, West Bengal (5 cases; CFR: 100%), Kozhikode and Malappuram, Kerala in 2018 (23 cases including confirmed and probable; CFR: 91%), Ernakulum, Kerala in 2019 (a single case-survived) and Kozhikode, Kerala in 2021 (one case, CFR: 100%).
The following factors may contribute to the risk associated with this outbreak:
· The exposure of the first case in this outbreak remains unknown;
· The presence of a bat population which has been reported to harbor NiV and therefore acts as a potential source of infection;
· High reported case fatality rate (33.3%) and high number of contacts; and
· The absence of Nipah virus-specific therapeutics and vaccines.
At the same time, the current outbreak is not entirely unexpected and is the third outbreak in Kozhikode district and fourth in the state of Kerala. Current cases are clustered and epidemiologically linked to the first case, and cases are localized to Kozhikode district. Public health teams and healthcare workers in Kozhikode have prior experience in managing outbreaks of NiV infection. The state government has rapidly established response measures to contain the spread of the outbreak and through enhanced surveillance and contact tracing measures, more than 1,000 contacts have been identified and are under monitoring. All high-risk contacts will be tested.
WHO Recommendations
In the absence of a vaccine or licensed treatment available for NiV, the only way to reduce or prevent infection in people is by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to NiV. Case management should focus on the delivery of supportive care measures to patients. Intensive supportive care is recommended to treat severe respiratory and neurologic complications.
Public health educational messages should focus on:
Reducing the risk of bat-to-human transmission
Freshly collected date palm juice should be boiled, and fruits should be thoroughly washed and peeled before consumption. Fruits with signs of bat bites should be discarded. Areas where bats are known to roost should be avoided. The risk of international transmission via fruit or fruit products (such as raw date palm juice) contaminated with urine or saliva from infected fruit bats can be prevented by washing them thoroughly and peeling them before consumption.
Reducing the risk of animal-to-human transmission.
Natural infection in domestic animals has been described in farming pigs, horses, and domestic and feral cats. 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. In endemic areas, when establishing new pig farms, considerations should be given to the presence of fruit bats in the area and general, pig feed and pig sheds should be protected against bats when feasible. Samples taken from animals with suspected NiV infection should be handled by trained staff working in suitably equipped laboratories.
Reducing the risk of human-to-human transmission.
Close unprotected physical contact with NiV-infected people should be avoided. Regular hand washing should be carried out after caring for or visiting sick people. Healthcare workers caring for patients with suspected or confirmed infection, or those handling their specimens, including trained staff working in suitably equipped laboratories, should implement standard infection prevention and control precautions at all times. Case management should focus on the delivery of supportive care measures to patients. Intensive supportive care is recommended to treat severe respiratory and neurologic complications. Safe burial practices are required for all confirmed and suspected NiV-infected cases.
Infection prevention and control
In health care settings, patients who are suspected of Nipah virus should be isolated in well-ventilated single rooms with dedicated patient equipment and toileting. Patients with suspected Nipah virus should not be placed in cohort rooms. Health workers interacting with patients with Nipah virus should use Contact and Droplet precautions when caring for patients with Nipah virus. Contact, Droplet, and Airborne precautions should be used, including placement of a patient in an airborne isolation room when aerosol-generating medical procedures are performed. If airborne isolation rooms are not available, a well-ventilated single room with windows open if using natural ventilation and doors to corridors closed should be used. Cleaning and disinfection of all surfaces in patient rooms housing suspected or confirmed patients with Nipah virus should occur at least once daily. After cleaning with soap and water, a 0.5% sodium hypochlorite solution disinfectant should be applied to surfaces, remaining untouched for 5 minutes contact time. Immediate cleaning and disinfection, as well as high touch surface cleaning, should be performed whenever a spill of blood or body fluid occurs. WHO infection prevention and control advice when caring for patients with Nipah virus infection is currently under review and is pending update. Health facilities should be equipped with enhanced water, sanitation and hygiene services to meet the needs of staff, patients and caregivers. Safe waste management practices should be adhered to by the healthcare facilities.
WHO advises against the application of any travel or trade restrictions on India based on the current information available on this event.