NEW YORK (BLOOMBERG) - New evidence from Europe and the United States suggests that younger adults aren't as impervious to the coronavirus that's circulating worldwide as originally thought.

Despite initial data from China that showed elderly people and those with other health conditions were most vulnerable, young people - from 20-somethings to those in their early 40s - are falling seriously ill.

Many require intensive care, according to reports from Italy and France. The risk is particularly dire for those with ailments that haven't yet been diagnosed.

"It may have been that the millennial generation, our largest generation, our future generation that will carry us through for the next multiple decades, here may be a disproportional number of infections among that group," Dr Deborah Birx, the White House coronavirus response coordinator, said in a press conference on Wednesday (March 18), citing the reports.

The data bears out that concern.

In Italy, the hardest hit country in Europe, almost a quarter of the nearly 28,000 coronavirus patients are between the ages of 19 and 50, according to data website Statista.

Similar trends have been seen in the US.

Among nearly 2,500 of the first coronavirus cases in the US, 705 were aged 20 to 44, according to the Centres for Disease Control and Prevention (CDC).

Between 15 per cent and 20 per cent eventually ended up in the hospital, including as many as 4 per cent who needed intensive care. A few died.

One of those younger adults is assistant professor of genetics Clement Chow of the University of Utah.

"I'm young and not high risk, yet I am in the ICU with a very severe case," Asst Prof Chow said in a tweet on Sunday.

"We really don't know much about this virus."

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According to his Twitter posts, Asst Prof Chow had a low-grade fever for a few days and then a bad cough that led to respiratory failure.

It turned out to be the coronavirus. He ended up on high flow oxygen in the ICU.

When he arrived last Thursday, he was the first patient there.

"Now there are many more," he tweeted.

Asst Prof Chow didn't give his age in the tweets, but his laboratory website indicates he graduated from college in 2003 and has two unruly children.

He didn't respond to an e-mail and Bloomberg was unable to independently confirm his status as a patient.

It's true that risk of death climbs precipitously with age.

While there were only 144 patients over age 85, as many as 70 per cent were hospitalised and 29 per cent needed intensive care, according to the CDC report.

One in four died, the agency said in the Morbidity and Mortality Weekly Report.

In the White House press conference on Wednesday, President Donald Trump implored younger people to stop reckless behaviour, such as partying, going to the beach and hanging out at bars.

Yet, as college campuses across the country close down and require students to leave, even the most conscientious young adults face a difficult choice.

Finding their academic years abbreviated and graduation plans shattered, many are driving or flying home, where they risk of exposing their parents and grandparents to Covid-19.

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The same concerns apply to young people starting out in big cities who suddenly find themselves under pressure to head back to their hometowns.

Ms Livia Calari's father has been begging her to come home for weeks. The 25-year-old and her boyfriend live in Brooklyn, New York, and have been nervously watching the warnings from officials intensify and the city they live in shut down.

But they're staying put, for now at least.

The couple has two cats they'd have to move. If they did hunker down with Ms Calari's father in Washington, DC, they would be asked to self-quarantine on a separate floor for two weeks.

Plus, the thought of accidentally bringing the virus worries them.

"I have a lot of anxiety, maybe irrationally, about bringing it to him," Ms Calari said of her father, who's 65. "I would feel awful."

After days of thinking over their options, they decided to stay in New York and re-evaluate if a lockdown gets to the point where they can't even leave their apartment to take walks.

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Infection-fighting officials are willing to go to unusual lengths to get the word out to young people where they congregate, including on the Pardon My Take podcast from Barstool Sports - one of the most popular sports shows with younger listeners.

Dr Anthony Fauci, the head of the National Institute on Allergy and Infectious Diseases, told the hosts how stressful the outbreak has been.

"You cannot imagine," he said. "You see what happened in China, you see what's happening in Italy. We have the virus in the United States, and we want to make sure by our efforts that we don't have that degree of disease and suffering that we are seeing in other countries."

And he called on young people to embrace the effort to protect themselves and the broader population.

"No one is invulnerable, but even if you are doing very well, you have to be a very important part of our national effort to contain the outbreak," Dr Fauci said.

"You are not a passive person in this. You are an important part of the active plan to contain this epidemic. We really do need you. This isn't something that can be successful without you."