Alert: Nipah Virus Infection in Kerala

6/6/2019

​[On behalf of MOH]

Dear Doctor,

1. On 4 June, the Kerala State Health Department of India reported one human case of Nipah virus (NiV) infection in the Ernakulam district, Kerala state. The case involved a 23-year-old male university student, whose samples were tested positive for NiV by the National Virology Institute in Pune. According to media reports, the case was undergoing treatment at a local private hospital in Kerala state, and was currently in a stable condition. Additional information regarding the case, including his exposure history, were unavailable at the time of reporting.

 

2. Public health measures including contact tracing, strengthening surveillance and infection control activities at health facilities, and risk communications to the community had been instituted to mitigate the spread of NiV infection in Kerala. As of 4 June, 86 contacts were under observation and had been asked to report to the nearest medical facility if they developed symptoms consistent with NiV infection. To date, four contacts, including two healthcare workers, had reported mild symptoms such as fever and sore throat. Risk to healthcare staff can be mitigated with good infection prevention and control practices.

 

RISK ASSESSMENT

 

3. This is the first case of Nipah virus infection reported in India in 2019, following the outbreak in Kozhikode and Malappuram districts of Kerala state in May 2018. The outbreak in 2018 comprised 19 cases including 17 deaths (case fatality rate: 89.5%). Fruit-eating bats were identified as the primary source of infection, and all subsequent cases occurred by person-to-person transmission through close contact with NiV cases. Prior to 2018, India had reported two other outbreaks in Siliguri and Nadia in 2001 and 2007 respectively.

 

4. The current case in Kerala is not unexpected, given that an NiV outbreak had occurred in the same state last year. As of 4 June, the case appears to be sporadic and localised, with no indication of community transmission. The necessary surveillance and control measures have also been put in place to mitigate the spread of NiV, and the Kerala state government had expressed confidence in controlling the situation. Travel volume from Kerala to Singapore is moderate (averaging approximately 6,000 per month), hence importation of a case into Singapore is possible. Nonetheless, alongside limited human-to-human transmissibility of NiV, the presence of well-established infection control practices would mitigate the risk of a serious public health impact in the event of an imported case in Singapore.

 

MANAGEMENT OF PATIENTS IDENTIFIED FOR INVESTIGATION

 

5. Patients with NiV infection generally present with fever, headache, dizziness and vomiting. Central nervous system (CNS) involvement occurs in the vast majority of symptomatic cases. A broad spectrum of neurological presentations has been reported, including aseptic meningitis, focal brainstem involvement, and diffuse encephalitis. Seizures and myoclonic jerks may occur in 20% of patients, while cerebellar signs are reportedly common. The disease is rapidly progressive for a majority of patients, with clinical deterioration leading to brainstem dysfunction and coma in 5-7 days.

 

6. Respiratory involvement occurs in up to 69% of cases, with the majority presenting with cough and dyspnoea. Chest X-ray changes of pneumonia (Singapore) and acute respiratory distress (India and Bangladesh) have been described.

 

7. As the signs and symptoms for NiV are non-specific, doctors should be alert to any traveller from NiV-affected regions with these presentations. In addition, doctors should always ask for travel history in patients presenting with signs and symptoms of encephalitis or respiratory distress, as they can be the result of many severe travel-related illnesses.

 

8. Patients who should be identified for investigation are:

  •  An acutely ill, febrile person with
    • Signs and symptoms of encephalitis OR
    • Acute respiratory distress

AND

With onset of symptoms occurring within 14 days of travel from a region (currently Kerala, India) with an ongoing Nipah virus outbreak.

9. Patient identified by primary care doctors for investigation with NiV whose conditions are medically stable should be sent to the following hospitals via the dedicated ambulance service at 6220-5298:

  • Persons aged 16 years and above (including pregnant women) will be sent to TTSH Emergency Department.
  • Children below the age of 16 years will be sent to KKH Children's Emergency Department.

 

10. Please call for the SCDF (995) ambulance if the patient is breathless or medically unstable. Please inform the ambulance operator that you are referring a suspect case of NiV.

 

NOTIFICATION UNDER THE INFECTIOUS DISEASE ACT

 

11. Nipah Virus Infection is a notifiable disease under the Infectious Diseases Act, and all cases of suspected and confirmed cases should be reported to MOH immediately. Please call the Surveillance Duty Officer of the Communicable Diseases Division at 9817 1463, followed by submission of the MD131 Notification of Infectious Diseases Form through the Communicable Diseases Live & Enhanced Surveillance (CDLENS) system at http://www.cdlens.moh.gov.sg, or by fax to 6221-5528/38.

12. Once again, we thank you for your support and co-operation as our first line of care in the community.

 

ANNEX

1. The NiV is an RNA virus that belongs to the genus Henipavirus of the Paramyxovirus family. Its natural reservoir hosts are fruit bats (Pteropus spp.) and possibly other species of bats. The virus was first discovered in March 1999, near the end of a large outbreak in Peninsular Malaysia that started in September 1998. Pigs were the intermediate amplifying host in that outbreak. This outbreak spread to Singapore in February 1999, with 11 abattoir workers infected via live pigs imported from NiV-affected areas in Malaysia. The total number of recorded cases from the Malaysia-Singapore outbreak was 265 human cases with 105 deaths. No occurrence of human-to-human transmission were reported in the Malaysia-Singapore outbreak. No new cases (neither swine nor human) have been reported from Malaysia and Singapore since May 19999.  NiV was first recognized in Bangladesh in 2001 and nearly annual outbreaks have occurred in that country since, with disease also identified periodically in eastern India (2001, 2007). In Bangladesh and India, there was no involvement of pigs in NiV transmission as was observed in Malaysia and Singapore. Consumption of raw date palm sap contaminated by fruit bats was the primary source of human infection. Limited human-to-human transmission of NiV among family and care givers of infected NiV patients through close contact with their secretions and excretions was also documented.

 

2. The incubation period of the NiV in humans is between 4 to 45 days, with >90% of symptoms developing between 4 and 14 days after exposure to the virus. Asymptomatic and mild infections have been reported in well-investigated outbreaks, but only a minority of infected persons (<10%) were found to be truly asymptomatic.

 

3. 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 important to work-up and manage suspect cases as for more common causes of encephalitis (including Japanese encephalitis virus and rickettsial infections from Kerala) or acute respiratory distress according to local guidelines until the diagnosis of NiV infection is confirmed.

 

4.  Patients with Nipah virus infection generally present with fever, headache, dizziness and vomiting. Central nervous system (CNS) involvement occurs in the vast majority of symptomatic cases. A broad spectrum of neurological presentations has been reported, including aseptic meningitis, focal brainstem involvement, and diffuse encephalitis. Seizures and myoclonic jerks may occur in 20% of patients, while cerebellar signs are reportedly common. The disease is rapidly progressive for a majority of patients, with clinical deterioration leading to brainstem dysfunction and coma in 5-7 days. In survivors, relapsing and late-onset encephalitis (up to 11 years in the longest known case) are distinguishing features of Nipah virus infection, occurring in up to 20% of cases. MRI brain in patients with CNS involvement typically demonstrate multiple small, discrete, hyperintense lesions present in the cerebral cortex, subcortical and deep white matter. Disseminated multifocal and confluent lesions in both cortex and white matter were also observed in cases in Bangladesh. CSF is abnormal in the majority of patients showing lymphocytic pleocytosis and elevated protein.

 

5. The estimated case fatality rate according to the World Health Organization is between 40% and 75%. The case fatality rate in a number of reported outbreaks in Bangladesh and India have exceeded 75%, but may reflect late presentation of cases. Up to 30% of survivors are left with persistent neurological deficits, and psychiatric features including depression and personality changes have also been described post-infection.

 

6. Clinical management is supportive. There is no specific anti-viral treatment and no commercially available vaccine at present. Patients who are under investigation or confirmed to have Nipah virus infection should be isolated and should strictly be placed on contact and droplet precautions - healthcare staff should don personal protective equipment and surgical masks when attending to these patients. N95 masks should be worn by healthcare staff when performing aerosol-generating procedures.

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