Long COVID may be affecting far more Americans than current estimates suggest, with a study published last week in JAMA Network Open estimating that roughly one in six people infected with SARS-CoV-2 develop the condition, and nearly 90% go on to experience chronic health problems.

For the study, a team led by researchers at Massachusetts General Hospital analyzed health record data from 457,950 adults treated for COVID-19 (also known as postacute sequelae of SARS-CoV-2 infection, or PASC) across 58 hospitals and clinics in New England, Southeast Texas, Southern California, and Western Pennsylvania.

The researchers identified long COVID cases by detecting symptoms and conditions that emerged after infection and could not be explained by preexisting conditions.