When coronavirus was at its peak in India, many feared that it would collapse the fragile health system of the country. At one point in time, it seemed that India might surpass the United States with the highest number of COVID-19 cases. However, the number started plummeting from September, leaving experts stumped. The country is recording 11,000 new cases per day as compared to around 100,000 cases when the pandemic was at its peak.

The experts, as quoted by ABP News in a report, have suggested many possible reasons behind this sudden drop. According to them, while some areas may have developed herd immunity, others might have pre-existing immunity from the COVID-19 virus.

As per the Indian government, the dip in cases may also be partly attributed to the mandatory mask-wearing in public places in India. However, experts suggested though mask compliance is not being followed in some areas, the decline in cases is uniform.

One of the reasons could be herd immunity in some large areas, explains Vineeta Bal, who’s studying immune systems at India’s National Institute of Immunology. However, this doesn’t give immunity from being infected again. According to Bal, in a recent survey in Manaus, Brazil, 75 per cent of people had antibodies in October but the cases surged again in January.

According to the Indian health agencies, 270 million, or one in five Indians, had already been infected before the vaccination drive.“The message is that a large proportion of the population remains vulnerable,” said Dr. Balram Bhargava, the head of Indian Council of Medical Research. However, the virus has infected city-dwellers more than those living in villages.

“Rural areas have lesser crowd density, people work in open spaces more and homes are much more ventilated,” said Dr. K. Srinath Reddy, president of the Public Health Foundation of India, citing the reason behind the slow spread in villages.

Another possible reason explained by the experts is that throughout life, Indians are exposed to several infections and diseases, thus building up a stronger immune system. “If the COVID virus can be controlled in the nose and throat, before it reaches the lungs, it doesn’t become as serious. Innate immunity works at this level, by trying to reduce the viral infection and stop it from getting to the lungs,” said Jameel, of Ashoka University.