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CDC study sees coronavirus shifting to young adults, but warns of spread to more vulnerable older adults

Coronavirus testing in June in Cambridge.
Coronavirus testing in June in Cambridge.Erin Clark/Globe Staff

The US Centers for Disease Control and Prevention says in a new report that the coronavirus has been hitting younger adults harder in recent months, while warning that the disease can spread from that group to more-vulnerable older people.

Early in the pandemic, the incidence of COVID-19 was highest among older adults, the agency said Wednesday in a Morbidity and Mortality Weekly Report.

But during the period from June to August, COVID-19 incidence was highest in people age 20 to 29. They accounted for more than 20 percent of all confirmed cases, the report said.

And the virus won’t stop at young people, the agency emphasized.


“Across the southern United States in June 2020, increases in percentage of positive SARS-CoV-2 test results among adults aged 20–39 years preceded increases among those aged [60 years or more] by 4–15 days,” the report said.

“Increased prevalence of SARS-CoV-2 infection among younger adults likely contributes to community transmission of COVID-19, including to persons at higher risk for severe illness, such as older adults,” the report said.

Why young people? The report suggested younger adults might be at higher risk for exposure to the virus because they make up a large proportion of workers in frontline occupations, such as retail stores, public transit, child care, as well as “highly exposed industries,” such as restaurants, bars, and personal services “where consistent implementation of prevention strategies might be difficult or not possible.”

The report also suggested young adults' behavior might play a role because they might “be less likely to follow community mitigation strategies, such as social distancing and avoiding group gatherings.”

The report noted that COVID-19 is “not benign in younger adults, especially among those with underlying medical conditions, who are at risk for hospitalization, severe illness, and death.”

The report said that “emphasis should be placed on targeted mitigation strategies to reduce infection and transmission among younger adults,” including:


- Age-appropriate prevention messages;

- Restricting in-person gatherings and events;

- Recommending mask use and social distancing in settings where persons socialize;

- Implementing safe practices at on-site eating and drinking venues; and

- Enforcing protection measures for essential and service industry workers.

“Given the role of asymptomatic and presymptomatic transmission, all persons, including young adults, should take extra precautions to avoid transmission to family and community members who are older or who have underlying medical conditions," the report said. "Strict adherence to community mitigation strategies and personal preventive behaviors by younger adults is needed to help reduce their risk for infection and minimize subsequent transmission of SARS-CoV-2 to persons at higher risk for severe COVID-19.”

In mid-August, the World Health Organization also warned that young people were emerging as the main spreaders of the virus and the risk of spillover to vulnerable populations like the elderly and sick was increasing.

“More infected youth mean more possibility for contact with those at higher risk,” Gregg Gonsalves, a global health expert at Yale University, said Wednesday in a tweet. “In fact, my concern is not theoretical,” Gonsalves said, pointing to the CDC report.

“More cases in young people is concerning from a public health perspective even if they don’t get very sick. It can be a harbinger of more cases in older, more vulnerable people later on, as they can transmit the infection even if they’re relatively well. Plus, there are the rare younger patients who get quite sick themselves,” Dr. Paul Sax, clinical director of the division of infectious diseases at Brigham and Women’s Hospital, said in an e-mail.


Jeremiah Manion of the Globe staff contributed to this report.

Martin finucane can be reached at martin.finucane@globe.com.