If the findings are even close to accurate, 4 million dead would be India’s worst mass casualty event in modern history by far.

The true count of India‘s deaths amassed so far during the pandemic could be a staggering 10 times the official Covid-19 toll, likely making it modern India’s worst human tragedy by a substantial margin, according to the most comprehensive research yet on the ravages of the virus in the South Asian country.

Most experts believe India’s official toll of more than 414,000 dead is a vast undercount, but the country’s government has previously dismissed such concerns as exaggerated and misleading, a pushback that was likely politically motivated.

The report released on July 20 estimated excess deaths — the gap between those recorded and those that would have been expected — to be between 3 million to 4.7 million between January 2020 and June 2021. It said an accurate figure may “prove elusive” but that the true death toll “is likely to be an order of magnitude greater than the official count.”

The report, published by Arvind Subramanian, the Indian government’s former chief economic adviser, and two other researchers at the Center for Global Development and Harvard University, said the count could have missed deaths occurring in overwhelmed hospitals or while health care was delayed or disrupted, especially during the devastating peak surge earlier this year.

“True deaths are likely to be in the several millions, not hundreds of thousands, making this arguably India’s worst human tragedy since Partition and independence,” the report said.

(The Partition of the British-ruled Indian subcontinent into independent India and Pakistan in 1947 led to the killing of up to 1 million people as gangs of Hindus and Muslims slaughtered each other en masse.)

The report on India’s virus toll used three calculation methods: data from the civil registration system that records births and deaths across seven states, blood tests showing the prevalence of the virus in India alongside global Covid-19 fatality rates, and an economic survey of nearly 900,000 people done thrice a year.

Researchers cautioned that each method had weaknesses, such as the economic survey omitting the causes of death.

Instead, researchers looked at deaths from all causes and compared that data to mortality in previous years — a method widely considered an accurate metric.

While other nations are believed to have undercounted deaths in the pandemic, India is believed to have a greater gap due to it having the world’s second-highest population of 1.4 billion, and its situation is complicated because not all deaths were recorded even before the pandemic.

“India’s official Covid death count as of end-June 2021 is 400,000,” the report says. “The reality is, of course, catastrophically worse … What is tragically clear is that too many people, in the millions rather than hundreds of thousands, may have died.”

The report also estimated that nearly 2 million Indians died during just the first surge in infections last year and said not “grasping the scale of the tragedy in real time” may have “bred collective complacency that led to the horrors” of the surge earlier this year.

NOT CONFINED TO INDIA

How many people have died of Covid-19 since the pandemic began? The official global total as of this week: 4.1 million. However, everyone agrees that the true toll is far higher. The disparity, however, varies considerably from country to country.

Still, Covid death undercounts are happening almost everywhere. In the United States, the official toll is 625,000 but the real number is likely far higher, says Ali Mokdad of the Institute for Health Metrics and Evaluation (IHME) – as much as 300,000 more deaths than reported. The group’s website has a global rundown that estimates “excess mortality” in many countries during the pandemic.

As of mid-May 2021, officially reported Covid deaths worldwide stood at 3.3 million. Analysis shows, however, that the true number at that time was 7.1 million, more than double the reported figures. The reason is so-called “excess deaths.”

When counting “excess deaths,” a term which refers to the number of deaths from all causes during a crisis above and beyond what we would have expected to see under ‘normal’ conditions, the specific cause of death is not included as part of the data set.

During a health crisis like the pandemic, the assumption is that these additional deaths are part of the true Covid-19 toll, says Mokdad. They reflect not only those who died explicitly from the virus (the official count), but those who might have died, say, from heart disease or diabetes because they were afraid to seek treatment during lockdowns, and those who killed themselves due to pandemic stresses, he adds.

Indonesia and the Philippines will likely be other regional candidates for serious undercounting due to their geography – each country comprising thousands of islands – large populations, poor healthcare infrastructure, and other factors.

Currently, the official death toll for Indonesia stands at 76,200, while the Philippines is at 26,844. Studies through mid-May suggested Indonesia was likely undercounting at a factor of about 2.5, which would currently place its true toll at about 190,000 dead.

Malaysia, meanwhile, landed at an undercount ratio of between 1.75 and 2.0. Assuming the lowest end of that range, that would suggest the true death toll here is now closer to 13,000, rather than the 7,241 reported.

The unfortunate truth, of course, is that in a global pandemic that will stretch on for more than two years – and longer still for much of the developing world – we will never know the true toll. For now, we can only continue to stay the course, keep up the mass vaccination efforts, take reasonable precautions, and look out for each other.

Reports from the Associated Press and NPR contributed to this article.