July 24 (UPI) -- More than one-third of people with mild COVID-19 experience symptoms for up to three weeks after they receive a diagnosis, according to figures released Friday by the U.S. Centers for Disease Control and Prevention.
This includes more than 25% of young adults ages 18 to 34, agency researchers said.
Younger people are considered to be at lower risk for severe COVID-19, but they constitute a significant portion of new infections in many outbreak hotspots across the country.
"These findings indicate that COVID-19 can result in prolonged illness even among persons with milder outpatient illness, including young adults," the agency researchers wrote.
"Preventative measures, including social distancing, frequent hand-washing and the consistent and correct use of face coverings in public, should be strongly encouraged to slow the spread of [the disease]," they said.
The findings are based on a survey of 294 adults with mild COVID-19, conducted between April 15 and June 25, CDC researchers said. Participants were selected from 14 predominantly urban academic health systems in 13 states, they said.
Although 65% of respondents reported that their COVID-19 symptoms resolved within seven days, the rest -- 35% -- indicated that they persisted for between 14 and 21 days, the researchers said.
Cough was the most common "persistent" symptom in 43% percent of respondents, followed by fatigue in 35% and fever in 26%, they said.
Thirty-two percent of adults ages 35 to 49 and 47% of those 50 and older reported persistent symptoms, the researchers said.
More than half of people with at least one chronic health condition -- most commonly, high blood pressure, obesity or mental health disorders -- also said they experienced persistent COVID-19 symptoms, the researchers said.
However, nearly one in five young adults ages 18 to 34 with no chronic medical conditions said that they had persistent symptoms of the infection, according to the findings.
As a comparison, more than 90% of those diagnosed with the flu fully recover within two weeks, research shows.
"This report indicates that even among symptomatic adults tested in outpatient settings, it might take weeks for resolution of symptoms and return to usual health," the researchers wrote.