COVID-19 Got Younger in Summer 2020: Cases Among 20-Somethings Came Before Older Adults

By September 21, 2020, the United States had recorded more than 6,800,000 COVID-19 cases and more than 199,000 deaths. Early on, the disease hit older adults hardest. By summer, that had changed.

The shift, May–August 2020

CDC tracked three measures in all 50 states and D.C.: emergency department visits for COVID-like illness, positive SARS-CoV-2 tests, and confirmed cases.

• Incidence rose in every age group under 80 from May to July, most among people under 30.
• From June through August, people aged 20–29 had the highest incidence and made up more than 20% of all confirmed cases.
• ED visits and positive tests showed the same shift in every Census region, though the timing differed.

Median age across the three measures nationally. Image from CDC's report

Young adults first, older adults after

The South had regional outbreaks in June–July. In HHS Regions 4, 6 and 9, the share of positive tests among adults 20–39 started climbing an average of 8.7 days (range 4–15) before it climbed among people 60 and older — roughly one to three incubation periods.

That suggests younger adults were helping drive community spread to older people. The World Health Organization has reported similar patterns, and Europe saw the same age shift, its median case age falling from 54 to 39.

Median age by Census region. Image from CDC's report

Not just more testing

Could more testing of young people explain it? Probably not entirely:

• the median age of everyone tested fell after the age of positive cases did — infection drove testing, not the reverse;
• the age mix of people tested stayed fairly steady from June to August;
• percent positive kept rising as testing grew, especially among 20–39-year-olds in Regions 4 and 6;
• ED visits, which don't depend on testing, followed the same pattern.

Why young adults

• Many work in frontline jobs — retail, transit, child care, social services — and high-exposure industries such as restaurants, bars, entertainment and personal services, where prevention is hard.
• They may be less likely to keep their distance or avoid gatherings.
• More often mildly ill or symptom-free, they can spread the virus without knowing.
• And infection isn't harmless for them, especially with underlying conditions.

What it means

Younger adults need to follow mitigation strategies and personal precautions strictly, both for themselves and to protect older and medically vulnerable people. Targeted steps: age-appropriate messaging, limiting in-person gatherings, masks and distancing where people socialize, safe practices at restaurants and bars, and protections for essential and service workers.

Limits: case reports undercount infections; batch reporting created spikes; the data sources covered different places; regional averages can hide local differences; and 10- and 20-year age bands can mask groups such as college students.

Sources

Based on Tegan K. Boehmer, Jourdan DeVies, Elise Caruso and others, "Changing Age Distribution of the COVID-19 Pandemic — United States, May–August 2020," MMWR, volume 69, Centers for Disease Control and Prevention; a work of the United States government in the public domain.