Coronavirus: Dramatic drop in cases in India puzzles scientists

NEW DELHI – When the coronavirus pandemic began to spread India, it was feared that the virus could sink the fragile health system of the second most populous country in the world. For months infections increased at a high rate and at one point it looked like India would overtake the United States as the country with the most cases.

But infections began to decline in September and the country is now reporting around 11,000 new cases per day, up from a peak of nearly 100,000., which puzzled the experts.

They suggested many possible explanations for the sudden drop in almost every region, like the one some areas may have been granted herd immunity or Indians had pre-existing protection against the virus.

The government also said part of the drop was due to use of masks, mandatory in India and with heavy fines for breaking the standard in some cities. But experts point out that the situation is more complicated, as the decline is uniform despite the irregular use of face masks in some areas.

It’s more than an intriguing puzzle: Determining the reason for the drop in infections could help authorities control the virus in the country, where nearly 11 million cases and over 155,000 deaths have been confirmed. Some 2.4 million people have died around the world. “If we don’t know why, we might do something and not know it might cause a rebound,” said Dr Shahid Jameel, virus researcher at Asoka University in India.

Like other countries, India fails to identify all infections and its system for counting deaths from virus has been questioned. But the pressure on the country’s hospitals has also declined in recent weeks, another indicator of the decline in infections. When recorded cases surpassed 9 million in November, official figures showed that nearly 90% of intensive care beds with ventilators in New Delhi were occupied. The occupancy rate last Thursday was only 16%.

This success cannot be attributed to the vaccines, as India started administering the injections in January.. Predictions are expected to improve as more people get vaccinated, although experts are concerned about variants of the virus identified in other countries, which appear to be more contagious and more resistant to certain treatments and vaccines.

One possible explanation for the decline in cases is that some large areas have achieved collective immunity, el umbral en el que suficiente gente ha desarrollado inmunidad al virus, ya sea por haber enfermado o por haber sido vacunado, como para que los contagios empiecen a caer, explicó Vineeta Bal, que estudia el sistema inmunológico en el Instituto Nacional de Inmunología de India.

But experts have warned that even though the decline in some areas is due to herd immunity, the population as a whole remains vulnerable and must maintain precautions.

This caveat has been underscored by recent research showing that people who got sick from one version of the virus could get a new variant again. Bal, for example, referred to a recent survey in Manaus, Brazil, which estimated that more than 75% of the city’s residents had antibodies to the virus in October, before cases resumed in January. “I don’t think anyone has a definitive answer,” he said.

The numbers are not that drastic in India. A nationwide survey of health authorities to detect antibodies determined that approximately 270 million people, or one in five Indians, had been infected with the virus before the start of vaccinations. It is well below the rate of 70% or more than what experts deem necessary for herd immunity to the coronavirus, although there is also no certainty on that figure.

“The message is that a large portion of the population is still vulnerable,” said Dr Balram Bhargava, who heads the country’s leading health research organization, the Indian Council for Medical Research.

But the survey gave no clue about the decline in infections. He indicated that more people had been infected in towns than in towns and the virus was moving more slowly through rural areas in the interior. “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, regardless of the threshold, and also limit contagion with masks and social distancing, and therefore have a decrease in cases, then maybe the low speed at which it is spreading the virus in rural India may help explain declining cases, suggested Reddy.

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

“If Covid-19 can be controlled in the nose and throat, before it reaches the lungs, it doesn’t get so bad. Innate immunity works at this level, trying to reduce the viral infection and prevent it from reaching the lungs, ”said Jameel, from Ashoka University.

Despite the good news in India, the appearance of new variants added another challenge to efforts in this country and others to contain the pandemic. Scientists have identified several mutations in India, some of which are attributed to infections in people who had previously suffered from previous versions of the virus. But they continue to study the implications for public health.

Experts are investigating whether Variants could fuel case boom in southern Kerala state, once seen as a model in the fight against the virus. It now has nearly half of the active cases of Covid-19 in India. Government-funded research suggests there may be a more contagious version of the virus in the region, and efforts are underway to sequence its genome.

As reasons for India’s success unclear, experts fear people are letting their guard down. Much of the country has returned to normal life. In many cities, you see open markets, crowded roads, and almost full restaurants.

“With the numbers reduced, I think the worst of Covid-19 is over,” said MB Ravikumar, an architect who recovered after being hospitalized last year. “We can all breathe a sigh of relief.”

Maybe not, said Jishnu Das, a health economist at Georgetown University who is advising the state of West Bengal on managing the pandemic. “We don’t know if it will come back after three or four months.”he warns.

AP

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