30% of people with COVID-19 experience symptoms up to 9 months later

A woman sitting on a bed looking tired.
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Nearly one-third of people with COVID-19 experience lingering symptoms up to nine months after their diagnosis, even if they initially had a mild case, a small new study suggests.

The study researchers, from the University of Washington, analyzed information from 177 people in the Seattle area with confirmed COVID-19 infections who were followed for three to nine months after their diagnosis. (The average follow-up time was six months.) Most participants — 150 people, or 85% of the study group — had a mild case of COVID-19 and were not hospitalized; 11 participants (6%) were asymptomatic; and 16 participants (9%) were hospitalized.

Overall, 32.7% of patients with mild cases and 31.3% of hospitalized patients reported having at least one persistent symptom that lingered at least three months after diagnosis.

Related: 'We just had no answers': COVID-19 'long-haulers' still learning why they're sick

The most common persistent symptoms were fatigue, reported by 13.6% of participants overall, and loss of smell or taste, also reported by 13.6% of participants, the authors said. About 13% of participants experienced other persistent symptoms, including muscle aches, breathing trouble, cough and brain fog.

"Our research indicates that the health consequences of COVID-19 extend far beyond acute infection, even among those who experience mild illness," the authors wrote in their paper, published Friday (Feb. 19) in the journal JAMA Network Open.

The authors also asked participants about their quality of life after being infected, and 30% of participants reported worse quality of life compared with before their infection, including 8% who reported problems with daily tasks, such as chores.

"What's clear is that you can do well initially, but then over time develop symptoms that are quite crippling in terms of fatigue," study senior author Dr. Helen Chu, associate professor of medicine, Division of Allergy and Infectious Diseases, at the University of Washington School of Medicine, said in a statement.

The study is one of the longest follow-ups of people with COVID-19. However, the study was limited because it included a relatively small number of participants from a single location. Still, with millions of cases worldwide, "even a small incidence of long-term debility could have enormous health and economic consequences," the authors wrote.

Exactly why some people develop these lingering symptoms — sometimes called "long COVID" — is unclear. "Is it some sort of immune activation, some sort of inflammation or the development of autoimmunity?" asked Chu, who added in the statement that she and her colleagues will be analyzing blood samples from patients with COVID-19 to study this question.

Originally published on Live Science. 

Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.