India’s comparatively low death rates — both as a percentage of total cases and per million population — are something of a mystery. The Indian government has cited the figures repeatedly to reassure a worried populace, saying such statistics show the country is faring better than many others in the pandemic.

That optimism appears misplaced. Experts say government data on deaths is certain to be incomplete in a country where a large majority of people die in rural areas and without any medical attention, making them less likely to be tested or diagnosed. Already there are numerous signs that coronavirus deaths are being missed or misreported. Testing rates per capita in India remain low. 

India is not the only country with a high number of reported cases and relatively low official fatalities. While Russia has more than 750,000 confirmed coronavirus cases, the country has reported about 12,000 deaths, sparking suspicion over counting methods.

In an interview with CNN earlier this month, Kremlin spokesman Dmitry Peskov defended Russia’s low death rate. “Have you ever thought about the possibility of Russia’s health-care system being more effective?” Peskov asked.

Russia’s mortality rate, measured by the number of deaths against confirmed cases, is 1.6 percent. India’s stands at 2.6 percent. The rate in the United States is 3.9 percent. But experts caution that such figures are highly sensitive to testing rates and death reporting, so they have limited value.

The actual risk of dying of a coronavirus infection may be lower than such figures suggest because many cases appear to be asymptomatic and undetected.

In India, one factor that experts say may indeed be lowering the death toll is its predominantly youthful population. According to the most recent census, only 5 percent of Indians were 65 or older while more than half were under the age of 25. Although much remains unknown about the virus, studies have shown that older people are far more likely to experience severe or fatal outcomes. 

A clutch of alternate theories has sprung up to explain India’s lower number of deaths, including widespread exposure to a tuberculosis vaccine that may stimulate the immune system, a different strain of the virus circulating here, and an undiscovered immunological or genetic factor present in the population. None are yet supported by evidence, experts say.

Meanwhile, the outbreak in India shows no sign of slowing, pushing some states and cities to reimpose lockdowns lifted weeks ago. Both the number of daily cases and daily deaths are rising and setting fresh records. India could be facing a “slow time bomb” as the virus continues to spread, said Prabhat Jha, an epidemiologist at the University of Toronto.

Jha previously led a major study to ascertain the causes of a million deaths in India, and he said a similar large-scale effort is needed if the country is to understand the true scope of infections. “The only way to walk out of this pandemic will be better data, and it’s not being collected,” Jha said.

Even in developed countries, the full extent of deaths linked to covid-19, the disease caused by the novel coronavirus, has not been reflected in official statistics. Instead, experts have attempted to analyze “excess deaths” — the ways in which overall deaths have deviated from prior years — as a proxy for the impact of the pandemic.

The Washington Post contacted officials in four of India’s largest cities — Mumbai, Delhi, Chennai and Kolkata — to obtain data for total deaths in each month from March to June for 2019 and 2020. Only Mumbai provided full and up-to-date figures. (Kolkata provided none.)

In Mumbai, the first city in India to be swamped by a wave of coronavirus cases, overall deaths in March were actually lower than in the same month in 2019. Officials say the decrease was likely due to the strict nationwide lockdown, which reduced deaths from such events as car accidents. In April, the deaths for the two years were roughly the same.

In May, however, total deaths in the city surged to 12,963 compared to 6,832 in the same month a year before. The difference is larger than the number of coronavirus deaths registered in the city in May, which was 2,269. Some of the jump is because deaths from prior months — at the height of the lockdown — were registered later, said I.S. Chahal, Mumbai’s new municipal commissioner. Chahal said the city had also treated many patients from neighboring areas.

Authorities have made efforts to record coronavirus deaths properly, he added, even if it meant that the official mortality rate increased. In June, Chahal ordered hospitals and clinics to register any previously unreported deaths from covid-19 within the next 48 hours or he would shut them down. The result: More than 800 deaths added to the overall toll.

“We’ve been transparent,” Chahal said. “Let other states of India show this courage.”

In several Indian cities, reports have emerged from graveyards and crematoriums where staff say they are handling more confirmed and suspected deaths from covid-19 than the official figures reflect.

In the city of Vadodara in western India, the official figures show that the total number of coronavirus cases has increased by more than 2,000 since the start of June. But the number of deaths has barely budged, rising by just three from 57 to 60.

Meanwhile, just one of the city’s hospitals has recorded at least 100 coronavirus deaths, outstripping the official toll, according to a person with access to medical records who spoke on the condition of anonymity because he was not authorized to speak publicly on the matter.

Vinod Rai, the official in charge of the Vadodara’s coronavirus response, denied the allegation. The city’s figure is correct and includes “every single death” due to covid-19 according to Indian government guidelines, he said.

In normal times, an estimated 20 percent of deaths in India aren’t reported at all, according to government statistics, often because they occur at home and far from cities. The gaps in India’s data mean that the true number of covid-19 deaths is higher than the official figure, but no one knows by exactly how much in the absence of further research, said K. Srinath Reddy, the president of the Public Health Foundation of India, an independent initiative that conducts research and training across the country.

Reddy added there are also other factors probably lowering the number of deaths. They include India’s comparatively young population and the fact that the majority of citizens live in rural areas, where density is lower, providing fewer opportunities for the virus to spread.

More than half of India’s deaths are from seven large metropolises, Reddy said. These cities are “still battling it out,” he said. “The biggest imponderable is whether we can contain the spread from reaching other areas which are now relatively safer.”

Some experts say that even while acknowledging the deficiencies in India’s data, they’re struck by the way its relatively low deaths per million is shared by other countries in South Asia and Southeast Asia, including Pakistan and Bangladesh.

“One can always say that this country or that country is fudging its data, but all countries cannot be fudging data at the same time,” said Shahid Jameel, a virologist and chief executive of the DBT/Wellcome Trust India Alliance, a public health foundation. He hopes to see further research into whether different populations have divergent immune responses to the virus.

Raul Rabadan, a professor of systems biology at Columbia University and the author of a recently released book on understanding the coronavirus, said he had not seen any convincing evidence yet that prior exposure to other viruses improved a person’s response to this one. He also said mutations in the virus have not been shown to change its lethality.

Teasing out which factors are responsible for variations in death rates is challenging even within the same country, let alone internationally, Rabadan said. India and the United States, for instance, differ in their health-care systems, their methods for reporting deaths, their criteria for coronavirus testing, the ethnic makeup of their populations and the age distribution of their citizens.

India’s seemingly lower death rates are “a paradox,” said Rabadan. But “I would be cautious.”

Taniya Dutta in New Delhi and Isabelle Khurshudyan in Moscow contributed to this report.