A youth under the age of 18 has become the first minor in the U.S. to die in the COVID-19 pandemic, Los Angeles County health officials reported Tuesday.

The youth was one of three new deaths reported by the department Tuesday. Health officials said the unidentified minor was from Lancaster, California but not provide other details, such as whether or not the youth had underlying health conditions.

"Tragically, one of the people who died was a person under the age of 18, a devastating reminder that COVID-19 infects people of all ages," said Public Health Director Barbara Ferrer at a press conference.

In Los Angeles County, there have been 256 new cases in past 48 hours, with 662 cases in the county total. Eleven people have died in the county to date.

People between 18 and 40 years old make up 42% of positive cases, Ferrer said.

The large percentage of younger people testing positive for the virus is even more stark than a Centers for Disease Control and Prevention report released last week which found that 1 in 5 U.S. cases were among people ages 20 to 44.

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That data still found older Americans face a higher risk of hospitalization, admission to an intensive care unit or even death.

Only nine of the 44 known deaths in the report were among those between ages 20 and 64, and no one under 19 was known to have died at that time.

"This virus is impacting the entire population, and it's something the entire population should be responding to," Dr. Wayne Tsuang, a pulmonary and critical care physician at the Cleveland Clinic told USA TODAY.

The data set the CDC used is limited and does not account for underlying medical conditions. Many more young adults could have COVID-19 with mild symptoms not requiring hospitalization and without their cases being tracked by public health officials.