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Actual number of COVID-19 cases is 12 times higher than reported, with 50 percent more deaths, says MIT study

A Boston EMS ambulance crew wheeled in a patient to Mass. General Hospital from an ambulance in April. While COVID-19 numbers have been decreasing in Massachusetts, cases have surged in parts of the world, including in the South and West of the United States.John Tlumacki/Globe Staff

The true number of COVID-19 cases around the world is roughly 12 times the official count, and the number of deaths is 50 percent greater, according to a study by Massachusetts Institute of Technology researchers, who contend that a swifter response could have prevented one-third of fatalities.

The paper, which relied on test results and other data from 84 hard-hit countries with a total population of 4.75 billion, concluded that cases are vastly undercounted in large part because, the researchers say, about half of infected people have few or no symptoms.

The authors estimate there have been 88.5 million coronavirus cases in the 84 countries and 600,000 deaths through June 18, far more than what the World Health Organization and the US Centers for Disease Control and Prevention reported. Cases have surged in parts of the world since then, including in the South and West of the United States.


“The magnitude of [the] epidemic is widely under-reported with much variation globally,” says the 57-page paper, which is marbled with mathematical calculations, by researchers from the MIT Sloan School of Management. Several Latin American countries have had particularly high infection rates.

Like a number of research studies publicized during the pandemic, the paper has yet to be submitted to a journal for publication or subjected to peer reviews that could identify shortcomings or flaws.

Although the authors concluded that the true number of deaths is 50 percent higher than reported, they said the actual number of infections is so much greater than official tallies that the fatality rate may be lower than some had feared.

In the United States, for example, the researchers estimate that 1 percent of cases have been fatal. That may not seem large, but one of the coauthors noted it is roughly 10 times the fatality rate of the seasonal flu.


“That’s a very high risk,” said John Sterman, director of the MIT System Dynamics Group, in an interview, and the risk is higher for the elderly. “Are you willing to subject yourself or your family to a 1 percent risk of death? Most people would say no.”

Without a vaccine or a breakthrough in treatments, and with only modest improvements in public health policies to control the epidemic, the researchers estimate that there could be a total of 249 million cases of COVID-19 and 1.75 million deaths by next spring in the 84 countries.

The study corroborates other recent reports that the official number of infections and deaths have been undercounted.

Last Friday the CDC said the number of coronavirus infections in many parts of the United States is more than 10 times the reported rate.

Experts have cited a variety of reasons for the undercounting: Many coronavirus cases are asymptomatic, people have struggled to get tested, and some deaths were attributed to other causes in the absence of testing.

Stephen Eubank, a professor at the Biocomplexity Institute and Initiative at the University of Virginia, said he had read a copy of the paper and found the conclusions well supported. He said he wouldn’t be surprised if the fatality rate from COVID-19, though higher than that for other infectious diseases, turns out to be not as high as some feared.

“Especially in the early days of our experience of a novel disease, the case fatality rate is always biased upward because you don’t know what the denominator is,” he said, referring to the number of people infected.


The MIT researchers included any country with at least 1,000 confirmed cases by June 18 and enough reliable testing data to interpret the results. Two countries battered by the virus, China — where COVID-19 first surfaced in December — and Brazil, were not included because there was insufficient reliable data.

The nations with the highest estimated percentage of populations infected to date, according to the MIT researchers, include Ecuador (18 percent), Peru (16.6 percent), Chile (15.5 percent), Mexico (8.8 percent), Iran (7.9 percent), Qatar (7.3 percent), Spain (7.1 percent), the United States (5.3 percent), the United Kingdom (5.2 percent), and the Netherlands (4.8 percent).

The paper, called “Estimating the Global Spread of COVID-19,” contends that tougher policies to reduce transmission of the disease after WHO declared it a pandemic on March 11, along with extensive testing, could have prevented 197,000 deaths, nearly a third of the estimated fatalities.

Now, however, future cases and deaths depend less on testing and more on the willingness of communities and governments to reduce transmission by limiting contact between people and through steps such as wearing masks, the authors wrote.

“Once you’ve got a high prevalence of the virus in the community, the magnitude of the testing and tracing you’d have to do is overwhelmingly large compared to the testing capabilities we have,” Sterman said.

Jonathan Saltzman can be reached at