Kerala Battles Renewed Nipah Virus Threat

Two Deaths Reported as 571 Are Under Surveillance

Kerala is once again grappling with the deadly Nipah virus (NiV), with two fatalities reported in July, intensifying public health concerns across the state.

Rising Case Count and Contact List

An 18-year-old woman in Malappuram and a 57-year-old man in Palakkad succumbed to the virus. The latest outbreak has placed 571 individuals on the Nipah contact list, underscoring the aggressive nature of the disease.

Understanding the Nipah Virus

NiV infection is a zoonotic illness, meaning it can transmit from animals to humans. Kerala has documented ten such “spillover” events since 2018, with four occurring this year alone. The virus can also spread through contaminated food or direct human-to-human contact. Fruit bats of the Pteropodidae family are identified as the natural hosts of NiV.

Global Risk and Vaccine Development

The Coalition for Epidemic Preparedness Innovations (CEPI) estimates that Nipah virus potentially poses a risk to 2 billion people worldwide. Promisingly, two vaccines against the virus are slated to enter human clinical trials in Bangladesh next year.

Laboratory Challenges and Biosafety

Testing for Nipah virus requires stringent laboratory conditions due to its high fatality rate, which can range from 40% to 75%. The European Centre for Disease Prevention and Control mandates specific biosafety levels, with propagation and isolation of the virus requiring the highest biosafety level 4 (BSL-4) facilities.

Kerala’s Research and Resilience Efforts

In 2023, Kerala established a One Health Centre for Research and Resilience in Kozhikode. Anish T.S., an expert in infectious disease epidemiology and nodal officer at the center, highlighted the importance of independent spillovers over widespread outbreaks. He noted that approximately 60% of past Nipah cases in Kerala were hospital-acquired, emphasizing the need for interventions like mask-wearing within healthcare settings.

“So if the cases have to be reduced, the intervention has to be in hospitals, which includes wearing a mask to avoid an infection.”

—Anish T.S., Nodal Officer, One Health Centre for Research and Resilience

Addressing Hospital-Acquired Infections

Anish T.S., who also serves on the Kerala State Medical Board of Nipah and the WHO’s Collaborative Open Research Consortium for Paramyxo viruses, pointed out that a significant portion of Nipah infections have occurred in hospitals. This highlights the critical role of infection control measures within healthcare facilities to curb the spread of the virus.

The Role of the One Health Centre

The One Health Centre, though currently a small unit, plays a crucial role in supporting existing health systems. Its work focuses on building resilience during inter-epidemic periods by creating guidelines and coordinating with local administrations to identify high-risk zones. The center collaborates with various agencies, including the Institute of Advanced Virology and government departments of Animal Husbandry and Environment, to foster a comprehensive “One Health” approach.

Challenges in Source Identification and Research

A significant challenge in Nipah research is the difficulty in pinpointing the exact source of transmission. While bats are known reservoirs, understanding the precise context of viral transmission remains elusive. Research involving high-risk pathogens like Nipah is further complicated by the limited availability of BSL-4 facilities in state institutions, with the National Institute of Virology (NIV) in Pune being a primary research hub.

Diagnostic Capabilities in Kerala

Kerala has made strides in diagnostic capabilities, with the government working to establish a fully functional BSL-3 facility in Kozhikode Medical College. Existing BSL-3 facilities are operational at Kozhikode and Manjeri Medical Colleges, as well as the Institute of Advanced Virology in Thiruvanthapuram. The NIV’s field Unit in Alappuzha also boasts a functional BSL-3 lab. The state leverages Truenat tests for rapid screening, complementing RT-PCR as the gold standard for Nipah diagnosis.

Independent Spillovers and Surveillance Strength

Recent analysis suggests that the current cases in Palakkad might be independent spillovers, a phenomenon not observed in earlier outbreaks. Anish T.S. believes that three independent spillovers are a more favorable outcome than a widespread outbreak. He hypothesizes that this could be attributed to robust surveillance mechanisms in Kerala, enabling the detection of sporadic events.

Understanding Bat Immunity and Transmission Cycles

Studies, including a serial survey of bats in Kerala by NIV, indicate a cyclical pattern of Nipah infection in bat roosts. Seroprevalence can fluctuate, suggesting periods of active viral transmission. The hypothesis is that immune roosts may offer lower chances of spillover, but immunity can wane over time, potentially leading to renewed transmission cycles.

Contact Tracing and Public Health Response

Contact tracing for Nipah is considered more manageable than for diseases like COVID-19, as transmission primarily occurs after symptom onset. The health system focuses resources on tracing individuals once a patient exhibits symptoms. Accredited Social Health Activists (ASHAs) play a vital role in community-level surveillance, reporting potential cases of Acute Encephalitis Syndrome (AES), which can sometimes be an indicator of Nipah infection.

Community Engagement and Prevention

Managing community response to Nipah requires clear communication and engagement. The district administration plays a key role in implementing containment measures. The virus’s potential to mutate and evolve makes early detection and intervention crucial to prevent the emergence of strains with pandemic potential.