Scientists confused by falling levels of coronavirus infections in India

Scientists are baffled by the relatively low rate of coronavirus infections in India after at one point it looked like it could outperform the United States as the country with the highest number of cases.

Infections started to plummet in September and the country is now reporting about 11,000 new cases per day, compared to a peak of almost 100,000, leaving experts perplexed.

They suggested many possible explanations for the sudden drop, seen in almost all regions, including that some areas of the country may have achieved herd immunity or that the Indians may have some pre-existing protection against the virus.

The Indian government has also partially attributed the drop in cases to the use of a mask, which is mandatory in public in India and the violations result in heavy fines in some cities.

But experts noted that the situation is more complicated, since the decline is uniform, although compliance with the mask is slow in some areas.

It is more than just an intriguing puzzle; determining what is behind the drop in infections can help authorities control the virus in the country, which has reported nearly 11 million cases and more than 155,000 deaths.

About 2.4 million people died worldwide.

“If we don’t know why, you may be unconsciously doing things that could lead to an outbreak,” said Dr. Shahid Jameel, who studies viruses at Ashoka University in India.

India, like other countries, loses many infections and there are doubts about how it is counting deaths from viruses.

But pressure on hospitals across the country has also eased in recent weeks, yet another indication that the spread of the virus is slowing.

When reported cases exceeded nine million in November, official figures showed that almost 90% of all intensive care beds with ventilators in New Delhi were full.

As of Thursday, 16% of these beds were occupied.

This success cannot be attributed to vaccinations, as India only started administering vaccines in January – but as more people get vaccinated, the outlook should look even better, although experts are also concerned about the variants identified in many countries which appear to be more contagious and make some treatments and vaccines less effective.

Among the possible explanations for the drop in cases is the fact that some large areas have reached herd immunity – a limit in which a sufficient number of people have developed immunity to the virus, when they get sick or are vaccinated, that the spread begins to decrease, he said Vineeta Bal, who studies the immune system at India’s National Institute of Immunology.

But experts warned that even though collective immunity in some places is partly responsible for the decline, the population as a whole remains vulnerable – and must continue to take precautions.

This is especially true because new research suggests that people who have become ill with a form of the virus can be infected again with a new version.

Bal, for example, pointed to a recent survey in Manaus, Brazil, which estimated that more than 75% of people there had antibodies to the virus in October – before cases increased again in January.

“I don’t think anyone has the final answer,” she said.

And in India, the data is not so dramatic.

A national screening of antibodies by Indian health agencies estimated that about 270 million, or one in five Indians, were infected with the virus before vaccination started – which is well below the rate of 70% or more than experts they say it may be the limit for coronavirus, although not even that is certain.

“The message is that a large proportion of the population remains vulnerable,” said Dr. Balram Bhargava, who heads India’s main medical research body, the Indian Medical Research Council.

But the research offered other information about why infections in India may be decreasing.

He showed that more people were infected in India’s cities than in their villages and that the virus was moving more slowly across the countryside.

“Rural areas are less densely populated, people work more in open spaces and houses are much more ventilated,” said Dr. K. Srinath Reddy, president of the Public Health Foundation of India.

If some urban areas are approaching herd immunity, wherever that limit is, and are also limiting transmission through masks and physical distance and are therefore seeing falling cases, then perhaps the low speed with which virus is passing through rural India may help explain declining numbers, suggested Dr. Reddy.

Another possibility is that many Indians are exposed to a variety of diseases throughout their lives – cholera, typhoid and tuberculosis, for example, are prevalent – and this exposure can prepare the body to mount a stronger initial immune response to a new virus. .