A Lancaster teenager whose death from the coronavirus was reported on Tuesday was in “good health” prior to falling ill, according to Los Angeles Mayor Eric Garcetti on Tuesday, March 24, though public health officials said the case was still under investigation and there may be an “alternate explanation for this fatality.”

Lancaster Mayor R. Rex Parris said the individual was a 17-year-old boy and confirmed he was in otherwise good health. The boy was sick for five days before he died, Parris said.

“It’s extremely upsetting,” Parris said over the phone Tuesday evening.

“This underscores the enormity of the challenges in front of us with this health crisis and how it can impact anybody and everybody,” Gov. Gavin Newsom said.

LA County public health officials, after making the announcement during their daily mid-day briefing, pushed out a terse follow-up statement in the afternoon, adding that the person’s death could have another explanation and was still under investigation.

“Though early tests indicated a positive result for COVID-19, the case is complex and there may be an alternate explanation for this fatality,” the health department wrote.

Parris said he found the county’s statement “nonsensical,” telling Southern California News Group the boy died at Antelope Valley Hospital of septic shock, a severe medical condition that occurs when the body has an overwhelming response to an infection.

The teen’s father, who drives for Uber, contracted the virus, Parris said. According to the Global Sepsis Alliance, COVID-19 can cause sepsis.

“Everyone should be truly horrified. We were told and we believed that this would not kill children and we learned today that is wrong,” Parris said. “How could this get any more horrible than it already is? That’s how.”

Little else was known about the individual who, if confirmed, represents the first known case of a minor under age 18 dying of COVID-19 in the United States — and one of only a few known worldwide. Health officials said earlier on Tuesday it was not known whether the individual had underlying health conditions.

While COVID-19, the disease that results from the coronavirus, kills mostly people over the age of 65, it hospitalizes people of various ages without discrimination.

“As a father and as an Angeleno my heart goes out to the family who tonight knows their child won’t be coming home,” Garcetti said. “To the young people out there this can hit you too. Know that your behavior can save a life and take a life and that life could be yours.”

Los Angeles County Public Health Director Barbara Ferrer said the news of the young person’s death was “a devastating reminder that COVID-19 infects people of all ages.”

“These are difficult numbers to report because behind these numbers,” Ferrer added, “are families and friends who are experiencing terrible loss.”

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A total of 11 people have died in Los Angeles County as a result of the coronavirus, as of Tuesday. Four additional deaths, including the teenager and another in Long Beach, were reported Tuesday along with 128 new cases in LA County. A total of 662 people were confirmed with the virus, though the actual number is likely much higher, health officials have said.

Demographic data on confirmed cases and even deaths is not completely available. In Los Angeles County, as of Tuesday, 10 confirmed cases were under age 18 and 268 or 42% were between the ages of 18 to 40. Roughly 17% of confirmed cases in LA County have been hospitalized, though their ages were not reported.

“This virus can in fact infect people across the board,” Ferrer said on Monday. “All people need to be vigilant and practice every directive that’s being issued.”

Half of those who tested positive in CA are 18 to 49. “Young people can and will be impacted by this virus,” Newsom said. “In fact young people disproportionately are the ones testing positive in California… With this tragic death it’s reminder for everyone to take this seriously.”

Data presented last week by the U.S. Centers for Disease Control and Prevention show that up to one-fifth of infected people ages 20 to 44 have been hospitalized, including 2% to 4% who required treatment in an intensive care unit. That was based on 4,226 confirmed cases in the US reported on March 16 and based on projections.

The paper identified just one case worldwide as of March 11 and zero cases nationally as of March 16 of a person under age 18 who died of the coronavirus, according to research on severe outcomes. A 14-year-old in China reportedly died since. And on Monday, the death of an 18-year-old with underlying health conditions from the coronavirus was reported in the United Kingdom. No other deaths of individuals under 18 have been reported by U.S. media as of Tuesday.

The biggest danger for young people getting the disease continues to be the risk they pose toward passing it onto someone older, possibly a parent or grandparent.

Overall, 80% of deaths associated with COVID-19 are people over the age of 65 with the highest percentage of severe outcomes among patients over 85 years old. The largest number of hospitalizations, roughly 36%, came from individuals between 65 and 84 years old. Less than 1% of hospitalizations were among people under 19, according to the CDC.

A study in the Journal Pediatrics, released in pre-publication on March 16, looking at children in China who contracted COVID-19 found more than 90% of all patients were asymptomatic, mild, or moderate cases. Only 6% had severe or critical symptoms.

World Health Organization Director-General Tedros Adhanom Ghebreyesus told a news conference that young people should nonetheless beware.

“Although older people are hardest hit, younger people are not spared,” Ghebreyesus said. “I have a message for young people: you are not invincible, this virus could put you in hospital for weeks or even kill you.”