NEW DELHI – When the coronavirus pandemic spread to India, it was feared that it would sink the fragile health system in the second most populous country in the world. Infections have increased dramatically for months, and at one point India seemed to be able to overtake the United States as the country with the highest number of cases.
But infections began to decline in September and now the country reports about 11,000 new cases a day, compared to a peak of almost 100,000, leaving experts perplexed.
They suggested many possible explanations for the sudden decline – seen in almost every region – including the fact that some areas of the country could have reached herd immunity or that Indians could have some pre-existing protection against the virus.
The Indian government has also partially attributed the decrease in cases of masked clothing, which is mandatory in public in India, and violations attract heavy fines in some cities. But experts have noted that the situation is more complicated, because the decline is uniform, even if compliance with the mask is marked in some areas.
It is more than an intriguing puzzle; Determining what is behind the decline in infections could 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 have died worldwide.
“If we don’t know why, you could unknowingly do things that could lead to an explosion,” said Dr. Shahid Jameel, who is studying viruses at Ashoka University in India.
India, like other countries, misses many infections and there are questions about how viral deaths are counted. But tensions over hospitals in the country have also dropped in recent weeks, further indicating that the spread of the virus is slowing. When cases exceeded 9 million in November, official figures showed that almost 90 percent of all fan critical care beds in New Delhi were full. On Thursday, 16 percent of those beds were occupied.
This success cannot be attributed to vaccinations, as India started administering vaccines only in January – but as more people receive a vaccine, the outlook should look even better, although experts are also concerned about the variations identified in many countries. which appear to be more contagious and make some treatments and vaccines less effective.
Possible explanations for the fall in cases include the fact that some large areas have reached herd immunity – the threshold at which enough people have developed immunity to the virus, through disease or vaccination, that the spread is starting to weaken, said Vineeta Bal, who studies the system. immune system at the National Institute of Immunology in India.
But experts have warned that while the immunity of herds 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 contracted a form of the virus could become infected again with a new version. Bal, for example, pointed to a recent survey in Manaus, Brazil, which estimated that more than 75 percent of people there had antibodies to the virus in October – before cases recurred in January.
“I don’t think anyone has the final answer,” she said.
And in India, the data is not as dramatic. A nationwide screening of antibodies by health agencies in India has estimated that about 270 million, or one in five Indians, were infected with the virus before vaccinations began – well below 70% or more. , which experts say could be the threshold for coronavirus, although this is not certain either.
“The message is that a large part of the population remains vulnerable,” said Dr. Balram Bhargava, who heads India’s leading medical research body, the Indian Medical Research Council.
But the survey provided other information on why infections in India could fall. It showed that more people were infected in Indian cities than in its villages and that the virus was moving more slowly through rural areas.
“Rural areas have a lower population density, 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 this threshold is – and also limit mask transmission and physical distancing and therefore see cases of falling, then maybe the low speed with which the virus passes through rural India can help explain the decrease in numbers, Reddy suggested.
Another possibility is that many Indians are exposed to a variety of diseases throughout their lives – cholera, typhoid and tuberculosis, for example, are widespread – and this exposure can lead the body to a stronger immune response and initially to a new one. virus.
“If the COVID virus can be controlled in the nose and throat, before it reaches the lungs, it does not become as severe. Innate immunity works at this level, trying to reduce the viral infection and prevent it from reaching the lungs, ”said Jameel, of Ashoka University.
Despite the good news in India, the rise of new variants has added another challenge to efforts here and around the world to bring the pandemic under control. Scientists have identified several variants in India, including some that have been accused of causing new infections in people who already had an earlier version of the virus. But they are still studying the implications for public health.
Experts are examining whether the variants could lead to an increase in the number of cases in the southern state of Kerala, which were previously considered a plan to fight the virus. Kerala now accounts for almost half of India’s current COVID-19 cases. Government-funded research has suggested that a more contagious version of the virus may be at stake, and efforts to sequence its genome are ongoing.
Given the reasons for India’s success, experts are worried that people will step down. Much of India has already returned to normal life. In many cities, markets are bustling, roads are crowded and restaurants are almost full.
“With the reduction in numbers, I feel that the worst of COVID is over,” said MB Ravikumar, an architect who was hospitalized last year and recovered. “And we can all breathe a sigh of relief.”
Maybe not yet, said Jishnu Das, a health economist at Georgetown University who advises the state of West Bengal on pandemic management.
“We don’t know if this will return in three or four months,” he warned.