NEW DELHI — When India’s biggest star, Amitabh Bachchan, announced on Saturday night that he had contracted the coronavirus, this country was shattered.

Mr. Bachchan, known as Big B, is not simply an enormously successful actor. He is one of India’s most revered figures. His face and rich, avuncular voice, dripping with gravitas, are everywhere, deployed in ads for household products, voice-overs at museums and countless public service campaigns. He was recently roped into doing a campaign on — what else? — the coronavirus.

With India getting walloped by the virus, Mr. Bachchan, 77, was still at it, trying to lift India’s spirits from what appeared to be his hospital room in a short video that was widely circulating on Sunday morning.

“They are trying times,” he says, appearing in the video with a white medical band tightly wrapped around his head. “Everyone is being worked to their absolute limits. There is always fear. Perhaps depression.”

“But please,” he urges, “do not despair, do not panic.”

India is now racking up more new reported infections each day — about 30,000 — than any other country except the United States and Brazil — and it is rapidly catching up to Brazil. India now has the third-highest number of infections after the United States and Brazil.

The authorities in several big Indian cities and states are reinstating quarantines after attempting to loosen things up to stimulate a critically wounded economy. The borders between states are being rigorously patrolled — again — with visitors shunted off to isolation centers.

International travel is still blocked. Hospitals are overflowing with the sick. Even nonvirus emergencies are being turned away. One pregnant woman was left to die in the back of an ambulance a few weeks ago after being rejected from eight different hospitals in 15 hours.

Narendra Modi, the prime minister, has been trying to lift spirits by saying in televised speeches that India is still doing better than richer countries, especially when it comes to the Covid-19 death rate. India has reported about 16 deaths from Covid-19 per million people versus the United States, Brazil, Spain and Italy, all of which have lost hundreds per million.

On Saturday night, Mr. Bachchan announced via Twitter — where he has 43.2 million followers — that he had tested positive. He was soon admitted to Nanavati Hospital, near the upscale Juhu neighborhood in Mumbai where he lives, overlooking the Arabian Sea.

“All that have been in close proximity to me in the last 10 days are requested to please get themselves tested!” he tweeted.

His son, Abhishek, also an actor, disclosed that he was positive as well. Both father and son appear to have only mild symptoms.

Suhasini Raj contributed reporting from Jaipur and Hari Kumar from New Delhi.