Coronavirus COVID-19 New York, USA
A worker uses a forklift to move a body outside of the Brooklyn Hospital on March 31, 2020 in New York, United States. Due to a surge in deaths caused by the Coronavirus, hospitals are using refrigerator trucks as make shift morgues. Stephanie Keith/Getty Images

COVID-19 is an old man's disease. That's the conventional wisdom. At least 95% of the total deaths in Europe are men older than 60, according to data from the World Health Organization (WHO). COVID-19 is also a grandfather killer in China where close to 30% of its 3,300 fatalities are men older than 60.

In the United States, the estimated mortality rate is 10% to 27% for those ages 85 and over; 3% to 11% for those ages 65 to 84; and 1% to 3% for those ages 55 to 64. The U.S. mortality rate is less than 1% for those ages 20 to 54.

The fatality profile in the United States for those ages 20 to 54, however, might be in error based on new data. Of the more than 16,000 deaths in the U.S. as of Thursday, at least 759 were people under age 50, according to a Washington Post analysis of state data. This means the fatality rate for this demographic has risen to 4.8% compared to the previous estimate of less than 1%.

Surprisingly, the Post also uncovered nine deaths among people younger than 20 in the U.S. What makes this data stunning are previous estimates there were fewer than 10 fatalities worldwide among people younger than 19. Two of these fatalities are Americans.

The Post also found at least 45 deaths among people in their 20s, about 190 deaths among people in their 30s, and some 413 deaths among people in their 40s. There were at least 102 other deaths in people younger than 50. The true number of deaths among young people is probably even higher, claims the Post.

Epidemiologists and other doctors are scrambling to find out why a lot more Americans under 50 are dying from this disease.

The fatality rate among adults under 50 varies by state. It's 0.8% in Massachusetts, 8% in Louisiana and 9% in Illinois. As might be expected, the largest number of COVID-19 deaths are in New York State, the epicenter of the U.S. pandemic. As of Thursday, the state reported 161,500 cases and some 7,100 deaths.

The Post reported six New York residents under the age of 20, 33 people in their 20s, 118 in their 30s and 265 in their 40s had died as of Wednesday. In Colorado, 247 people under 50 have been hospitalized. Of these patients, nine have died.

Data on more than 1,400 hospitalizations released Wednesday by the U.S. Centers for Disease Control and Prevention (CDC) shows 25% of people hospitalized with the disease were under age 50. Ominously, most of these people suffered from underlying conditions such as asthma, diabetes and hypertension.