Back in November, Ajeet Jain felt like he was living a nightmare. The large public hospital where he works in India’s capital was full of covid-19 patients, hundreds of them so ill they required intensive care. About 10 people were dying every day. Three months later, the situation is unrecognizable. The number of coronavirus patients at the hospital can be counted on one hand. Out of 200 ventilators, only two are in use. Hospitals treating covid-19 patients around the country report similar experiences. “It’s a big, big relief,” Jain said.
The apparent retreat of the coronavirus in India, the world’s second-most populous nation, is a mystery that is crucial to the future course of the pandemic. Just months ago, India was adding nearly 100,000 cases a day — more than any other country. On Tuesday, it reported only 8,635. That’s about the number recorded the same day by New York state, where the population is less than 2 percent of India’s.
Epidemiologists in India say that there is only one likely explanation for the decrease in new cases: The virus is finding it harder to spread because a significant proportion of the population, at least in cities, already has been infected.
The decline is not related to a lack of opportunities for transmission. India has fully reopened its economy, with elementary schools being the only major exception. Restaurants, malls and markets are bustling. Masks are common in some indoor settings and mandatory in Delhi and Mumbai, but in many parts of the country, they’re scarcely seen on the streets.
India has reported 10.8 million coronavirus cases in total, although that is likely to be a vast undercount. The results of a nationwide antibody survey of 28,600 people by the government released on Thursday indicated that more than 1 in 5 Indians — about 270 million people — had been exposed to the virus as of early January.
In major cities, infection rates are even higher. On Tuesday, Satyendar Jain, the health minister for Delhi, announced that a recent study of 28,000 people in India’s capital found 56 percent had coronavirus antibodies. Earlier antibody surveys of certain neighborhoods in Mumbai and Pune also found that a large proportion of the residents had been infected.
By comparison, a study published last month estimated that more than 14 percent of the population in the United States had coronavirus antibodies as of mid-November.
Such antibody surveys have proved sensitive for health officials in India. They indicate that the actual number of infections in the country is far higher than the official tally and that efforts to contain the spread of the virus in cities largely failed. The surveys also show that most cases of coronavirus infection went undetected despite a significant increase in testing.
India’s big cities probably have “reached the threshold of population immunity,” said Giridhar Babu, an epidemiologist at the Public Health Foundation of India. The virus will continue to spread, he added, but “the quantum of infected cases will not be the same.”
Epidemiologists are quick to add notes of caution. How new variants of the virus will affect infections in India is unclear, and vaccination remains critical to warding off a possible second wave. The variant first detected in Britain is already in circulation here, and experts say India needs to expand its genetic surveillance of cases to understand how mutations are spreading.
