Scientists have been left confused by the plummeting rate of coronavirus infections in India – particularly because the country was at one point on course for the biggest toll worldwide.

Nearly 100,000 infections were reported each day during India’s peak, but this has taken an unexplained tumble since September to around 11,000 a day.

Official figures in November also showed 90% of New Delhi’s critical care beds with ventilators were filled, whereas just 16% were full last Thursday.

Vaccines have so far been ruled out as a reason alone as the country’s jab program didn’t begin until January – although this is expected to brighten the outlook even further.

The Indian government has suggested compulsory mask-wearing in public may have helped, especially due to hefty fines that follow violations in some cities.

But experts say it can’t only be attributed to masks as declining case numbers appear to be uniform across the country, whereas mask-wearing fluctuates in different areas.

“If we don’t know the reason, you could unknowingly be doing things that could lead to a flare-up,” said Dr Shahid Jameel, who studies viruses at India’s Ashoka University.