Half of new Covid-19 cases are among people 40 and younger

While the coronavirus can more harshly impact people ages 60 and above, a new report indicates half of new Covid-19 cases are happening among people age 40 and under.

Dr. Judith Malmgren is an epidemiologist and president of HealthStat Consulting. She's also the lead author of the new report, which has not been peer-reviewed but is published on medRxiv.

It draws on state data from the beginning of March to early May.

She joined KUOW’s Angela King to discuss her findings.

Angela King: As you look at the data from the last few months, what changes are jumping out at you?

Dr. Judith Malmgren: In an eight-week time period, the age proportionality changed from 60 and older to under age 40. And I think this indicates that 20- to 39-year-olds who are active and social and out and about and somebody that you might interact with, if you're an older person, and they have the milder form of the disease, so maybe more likely to have asymptomatic disease, which would enhance spreading because they don't know they're sick. It's a fairly dangerous situation that we have right now.

So why do you think we're seeing these changes?

Efforts were made and the messaging was very strong, that person 60 years and older, and those with pre-existing conditions were at higher risk of adverse outcomes with coronavirus. And over time, that had a salutary effect. We had a decrease in incidence in those age groups and we also had a decrease in hospitalizations and deaths. However, over the same timeframe in Washington state and in King County, we noticed a plateau of cases. And what we found was that age 20 to 39 cases increased and percentage increased. And then the number actually started to decline but the percentage kept going up. So the rate of declining cases was not as great in the 20- to 39-year-olds, as it was in the older age groups. And the number of cases just continued to climb in the zero to 19-year-old age group.

We also looked at testing, because a lot of people say, well, we're testing more, so that's why there's more of these cases. But that's not true. Testing actually went down in these (younger) age groups and went up in the older age groups.

What could all of this mean for how the pandemic plays out?

Well, the pandemic is a big thing. I'm looking at a granular level. If we want to get out of the plateau, and we want to move to reopening, to do that we need to look at a granular level, we need to look at who, what, when, where are people getting sick, how is infection being transmitted, who's becoming infected.

Clarification, 6/2/2020: This post has been edited for transcription errors.