Before Nipah could spread: How AIIMS Kalyani’s midnight response, rapid testing and strict containment averted an outbreak

“What matters is swiftness of response and containment drills. All 196 contacts were line-listed and kept under surveillance. They were asymptomatic. All of them then tested negative,” he says.

As for the investigations, sequencing from the two confirmed cases showed Bangladesh genotype lineage, with 99% similarity to 2022 Bangladesh strains. Two out of 35 Pteropus medius bats tested positive for Nipah virus and 11 out of 26 bats tested IgG-positive for Nipah (evidence of past exposure). Environmental sampling of raw date palm sap and pot swabs from local vendor sites tested negative by RT-PCR. Excerpts:

What is Nipah virus and how does it spread?

Nipah is a zoonotic virus with high fatality and the ability to cause severe encephalitis and/or severe respiratory disease. Humans usually acquire infection via:

• Spillover from fruit bats through contamination of food/drink with bat saliva/urine — classically raw date palm sap (and sometimes contaminated fruit).
• Human-to-human transmission can occur through close contact with secretions/excretions, especially among caregivers and in healthcare settings. In Siliguri (2001), most infections were in hospital staff/visitors; in Bangladesh outbreaks, a substantial fraction has been linked to person-to-person spread.

But what most people need to know is that it is not “airborne like measles.” Transmission is mainly via close contact and body fluids, though airborne precautions may be needed during certain aerosol-generating procedures in hospitals.

Does it spread rapidly?

Usually, no. Nipah has caused clusters and outbreaks but it typically shows limited sustained community transmission. Most large spread events happen in household caregiving and healthcare settings when infection-control practices break down. There is a typical high spread from the index case but very low spread just after one generation of infection or the time gap between the time a person is infected and the time they infect another person.

That said, because it is a high-consequence pathogen, even a small cluster triggers strong containment measures.

What is the survival rate?

Nipah is associated with high case-fatality, often quoted as 40% to 90% depending on outbreak and setting. Bangladesh, which has had repeated outbreaks, has historically reported a very high case fatality rate or CFR (71.7%).

Due to high suspicion, early quarantine and early antiviral therapy, mortality in West Bengal is zero out of two proven cases. Both patients first developed fever followed by neurological deterioration (encephalitis) and respiratory distress. Both were intubated and ventilated. They were treated initially with ribavirin, then with remdesivir.

How did they acquire the infection?

There could have been a spillover from a probable primary case (55-year-old woman) who had a confirmed history of raw date palm sap consumption, developed fever, viral pneumonia and died on December 22. The two nurses were unprotected while caring for her and administering emergency procedures.

What is the recovery pattern in Nipah?

Survivors can recover fully but some may have neurological sequelae (e.g., weakness, seizures, cognitive/behavioural changes), requiring rehabilitation and follow-up. This is something we saw in Kerala, too.

Some Asian countries are screening Indians visiting — should we worry?

Screening of travellers is a precautionary public-health measure when a high-consequence pathogen is in the news. It does not automatically mean high community spread. Nipah doesn’t have community spread, and this kind of widespread testing is not recommended.

From an outbreak-control standpoint, what matters is:

• Whether there is ongoing unexplained transmission, and
• Whether contacts are being monitored and cases isolated promptly.

So, the risk to the general public is typically low, but health systems must remain vigilant for severe fever, respiratory and neurological syndromes.

What should people do to prevent it?

Follow the clear public advice supported by WHO and the outbreak experience:

• Avoid raw date palm sap/fresh palm juice (especially in winter harvesting season); avoid anything possibly contaminated by bats.
• Avoid partially eaten fruits and fruits found on the ground in areas with bat activity.
• Avoid close contact with anyone with fever, altered sensorium and severe respiratory symptoms; seek care early.
• Hospitals must comply with strict hygiene standards when it comes to tracking contacts and isolation. Strict droplet precautions must be implemented, especially during coughing, sneezing, or when performing aerosol-generating procedures.

What should the government do for prevention and preparedness?

Ensure early detection and surveillance, rapid lab testing with multi-sample strategy and fast turnaround. Use mobile/field BSL-3 labs during outbreaks. These biosafety labs are designed to study highly infectious and potentially lethal pathogens that can be transmitted through air. The systems are designed such that these pathogens do not accidentally escape through the ventilation system or with the scientists working inside.

Be rigorous about contact tracing and the 21-day follow-up rule from the last exposure. Ensure PPE gear, isolation beds and ICU readiness.

Monitor bat ecology and spillover risk; reduce exposure pathways (for example, insisting upon safer sap harvesting practices). WHO has noted repeated association with raw date palm sap in Bangladesh and India.