On Mar. 24, 2020, an international project aimed to enroll 500 COVID-19 patients to search for genetic mutations that make some people more vulnerable to severe infection. Hundreds of clinicians worldwide  banded together in an effort to study some types of severe cases of the new coronavirus disease.

The project, led by Howard Hughes Medical Institute (HHMI) Investigator Jean-Laurent Casanova at The Rockefeller University, sought to identify genetic errors that make some younger patients especially vulnerable to the virus that causes COVID-19, the infectious respiratory illness also known as coronavirus disease 2019.

Casanova aimed to enroll 500 patients internationally who meet three broad criteria: they’re less than 50 years old, have been diagnosed with COVID-19 and admitted to an intensive care unit, and have no serious underlying illnesses, such as diabetes, heart disease, or lung disease.

By studying these patients’ DNA, scientists may pinpoint genetic mutations that make some people more susceptible to infection. Such information could one day help doctors identify people who are most at risk of developing severe coronavirus disease, says Casanova, a pediatrician at Rockefeller. It could also offer clues for scientists searching for new therapeutics. For example, if patients’ cells aren’t making enough of a particular molecule, doctors may be able to offer a supplement as treatment.

That day may still be years away. “This is not a short-term effort,” Casanova says. Some scientists have hypothesized that COVID-19 might be a seasonal illness, with infections ebbing in the spring and summer, and then returning in the fall. But Casanova’s team is optimistic. They had already begun enrolling patients and have started sequencing their “exomes” – spelling out all of the DNA letters in every gene in a person’s genome. “We’re going to try to find the genetic basis of severe coronavirus infection in young people.”