In the months since the coronavirus outbreak emerged, experts have provided different estimates of the disease's mortality rate. Officials at the World Heath Organization previously reported a 3.4 percent death rate, while Dr. Anthony Fauci—a key member of the White House Coronavirus Task Force—estimated a rate of around 2 percent.

"If you look at the cases that have come to the attention of the medical authorities, in China, and you just do the math — the math is about 2 percent," Fauci told Congress earlier this month. "If you look at certain age groups, certain risk groups, the fatality is much higher."

According to a newly published study in The Lancet Infectious Diseases, the overall death rate for COVID-19 is at 1.38 percent for confirmed coronavirus cases; but when you take undiagnosed cases into account, the rate is .66 percent. Researchers came to this conclusion after analyzing clinically detected cases among Wuhan citizens and confirmed cases among those repatriated from the country. 

Per the study:

To estimate the infection fatality ratio we fitted to data on infection prevalence from international Wuhan residents who were repatriated to their home countries. Our age-stratified case fatality ratio and infection fatality ratio model was jointly fitted to the case data and infection prevalence data with use of Bayesian methods, using our previous estimate of the onset-to-death distribution as a prior.

However, experts stress that COVID-19 is still much deadlier than the flu—especially among older age groups. 

"There might be outlying cases that get a lot of media attention, but our analysis very clearly shows that at aged 50 and over, hospitalisation is much more likely than in those under 50, and a greater proportion of cases are likely to be fatal," said Azra Ghani, a professor at Imperial College London and an author of the study, in a statement.

According to data, the death rate among children younger than 9 is 0.00161 percent; 10-19 is 0.00695 percent; 20-29 is 0.0309 percent; and 30-39 0.0844 percent. The death rate percentage grows with the following group groups, with 4.28 percent rate among those in the 70s and a 7.8 percent among those 80 or older.

"Even though the fatality rate is low for younger people, it is very clear that any suggestion of COVID-19 being just like influenza is false," Shigui Ruan, a professor in the department of mathematics at the University of Miami, wrote in a statement.

On Tuesday, the U.S. death toll for COVID-19 surpassed 800—the most for a single day since the outbreak. There are now more than 184,000 confirmed coronavirus cases and 3,700 confirmed deaths in the country. Those figures are expected to significantly grow within the next two weeks.

During Tuesday's White House briefing, members of the Coronavirus Task Force projected 100,000 to 240,000 Americans could die from the disease—even with social distancing measures in place. 

"As sobering a number as that is, we should be prepared for it," Fauci told reports. "It will be difficult, not one is denying that we are going through a really difficult time right now ... We have to brace ourselves. In the next several days to a week or so we are going to continue to see things go up. We can not be discouraged by that because the mitigation is actually working and will work.”

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