They're the cases that stand out, because they don't seem to fit the coronavirus pattern: A 32-year-old nurse died of COVID-19 after spending several days on a ventilator at Harbor-UCLA Medical Center. A 25-year-old pharmacy technician who had seemed to be in good health had succumbed to COVID-19 in a Riverside County home.
It's enough to make you wonder: Is the coronavirus more dangerous to younger people than scientists initially thought?
When the outbreak took off in Wuhan, China, there was a distinct trend: The older the patient, the greater the risk of death. And as the virus spread around the world, that trend seemed to hold up. A study published in the medical journal Lancet that analyzed more than 70,000 cases from January and February found that the fatality rate for COVID-19 patients in their 30s was 0.15%, compared with 13.4% for those 80 and older.
But in the U.S., doctors on the front lines have noted strange and often alarming conditions in younger victims, including patients in their 30s and 40s dying of strokes after experiencing only mild COVID-19 symptoms. Children and teens have ended up in hospital intensive care units with symptoms of a rare inflammatory syndrome called Kawasaki disease that could be related to COVID-19, according to a bulletin released by the New York City Health Department this week.
For now, cases like these remain disparate pieces of a much larger puzzle. As scientists dig deeper, they hope to learn more about the role of age as a COVID-19 risk factor and why the disease is so dangerous to the elderly.
But in the meantime, they're seeing that younger victims are still more the exception than the rule, even in the U.S. Here's a closer look at what they know so far, and what they're still trying to find out.
– Age is a factor in deaths, but not in infections
Scientists generally agree that when it comes to age, the coronavirus doesn't appear to discriminate, though pinning down the infection rate will require far more widespread testing than has been done so far.
"Anyone at any age can become infected," said Dr. Timothy Brewer, an infectious disease specialist and epidemiologist at the University of California, Los Angeles. "But we are seeing very different outcomes in what happens after people are infected."
As the pandemic has grown, the risk of ending up in the hospital or dying has remained markedly higher for those in older age groups – a trend that's become even clearer over time.
Soon after the Centers for Disease Control and Prevention began monitoring the coronavirus' activity in the U.S., it found that for the week ending March 21, the COVID-19 hospitalization rate for those 65 and older was 10.4 per 100,000 people, compared with 1.9 hospitalizations per 100,000 people ages 18 to 49. By May 2, both figures had risen considerably – to 162.2 hospitalizations per 100,000 senior citizens and 26.2 per 100,000 younger adults – but the large gap remained.
COVID-19 hospitalization rates are lower in California, but they follow the same trend. The most recent figures from the CDC's COVID-NET surveillance network indicate that 56.9 out of every 100,000 Californians 65 and up had been hospitalized for COVID-19, compared with 10.9 out of every 100,000 Californians ages 18 to 49.
In many infectious disease outbreaks, such as seasonal influenza, the very young and the very old face the greatest risk of serious illness and death. Researchers are still puzzled as to why COVID-19's pattern is so one-sided, with infected children typically having only mild symptoms of the disease.
One potential explanation is that the immune systems of children are too immature to trigger the massive inflammatory response that can lead to septic shock, organ failure and other complications in some COVID-19 patients, experts say.
Another hypothesis is that there are so many other types of mild coronaviruses circulating among children that they have some kind of partial immunity against the SARS-CoV-2 coronavirus, the one that causes COVID-19.