Young adults and children appear to be increasingly contracting the new coronavirus in the United States, according to a new study.
Scientists found that half of those who had tested positive for Covid-19 in Washington state by early May were aged under 40, significantly more than at the initial stage of the outbreak.
Health authorities have been focused on elderly people and those with underlying conditions who are considered more likely to become severely ill or die from the disease.
In the study, epidemiologist Judith Malmgren and her team at the University of Washington analysed data from all 22 testing laboratories across the state. They found that young people had become more susceptible to the virus – especially in counties with a high proportion of the population aged between 20 and 39 – since early March.
The findings could point to progression of the pandemic in other areas, since “Washington state is the first in the United States with Covid-19 experience and [has] the longest outbreak timeline”, Malmgren said in a non-peer reviewed paper posted on preprint website medRxiv.org on Saturday.
It comes as the US – the worst-hit country by far – has started reopening after a months-long lockdown, with people flocking back to beaches, restaurants and bars. The scientists warned that given the increasing prevalence of Covid-19 among young people, the reopening could put them and their families at greater risk.
Washington state in January reported the first coronavirus case in the US – a traveller from Wuhan in China, where the outbreak was first reported late last year. Washington was also where the first confirmed cases of community transmission were detected in America. As a result, authorities in the state imposed one of the country’s earliest and toughest shutdowns, and by Saturday its tally of daily cases – 298 – was a fraction of the national total of more than 22,000.
Worldwide, the virus has infected more than 5.3 million people, with nearly 350,000 deaths.
While new cases have been declining in Washington state, the researchers found that the proportion of children and young adults confirmed with Covid-19 rose from 20 per cent on March 1 to 50 per cent early this month.
And there was “no decline in cases” in the 0 to 19 age group, Malmgren said in the paper. In contrast, the incidence of the disease among people aged 60 and older fell by 55 per cent from the peak of cases.
This fundamental shift in disease demography could bring new challenges in controlling the outbreak, the researchers said.
Younger people tended to have twice the number of close contacts with others than the elderly, according to a study last month from the Harvard T.H. Chan School of Public Health. They also often worked in sectors with high levels of public contact, and were more likely to flout infection control measures such as social distancing, according to the University of Washington researchers. They said young people – in better health and with stronger immune systems – were also more likely to become stealth carriers of the virus who did not show up at hospitals or testing facilities.
“The shift from older to younger population Covid-19 infection may mask a true decline in cases and the need for future health care capacity if the currently infected portion of the population is younger, less likely to report symptoms, and at less risk of a severe life-threatening disease requiring hospitalisation,” the researchers said.
But young people are also becoming critically ill or even dying from Covid-19. In New York, there have been reports of young patients who had been in good health and died from a stroke after contracting the disease. Some children have also developed a rare but severe inflammatory condition.
The trend of younger people contracting the virus has also been reported in other countries. In Brazil, doctors have said that half their patients were young, and many were dying – 15 per cent of deaths in the country were people aged under 50, which was 10 times the proportion in Europe, The Washington Post reported.
The situation was worse in Mexico, with nearly a quarter of deaths among people aged between 25 and 49, according to health authorities.
The US researchers concluded that as the number of cases rose among young people, they should be “included in the priority for identifying, controlling and stopping the spread of Covid-19”.
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