Even Mild Coronavirus Illnesses Can Have Lasting Effects: Study

SEATTLE — Coronavirus infections in patients with mild symptoms, or even no symptoms, can still have health effects that linger for several months, University of Washington researchers have found. A new study published Friday monitored 300 participants from the Seattle area for six to nine months and discovered some previously healthy adults experienced fatigue, loss of smell and taste, and other effects long after their initial diagnosis.

Although previous research has studied "long COVID," UW Medicine said its latest study ranks among the longest in duration, and its findings were unique since many of its participants were never hospitalized or seriously ill.

"Lingering symptoms are common in those who were sick enough to be in the hospital, as well as in those who really weren't sick at all when they were diagnosed," said Dr. Helen Chu, A UW Medicine professor and senior author of the study. "They didn't even need to be seen in a clinic or an emergency department."

According to researchers, 30 percent of the study's participants reported worse health and quality of life in the wake of the illness, and 8 percent said they were unable to perform simple chores, lift heavy objects or walk for more than a short period.

Researchers are still trying to answer the question of what causes long-term illness in some patients, including the possibility of immune activation or inflammation. Chu's team plans to analyze the blood samples from patients with lingering symptoms to learn more.

"This is what this post-COVID syndrome is looking like, but up until now we have not had the numbers or proportions of people who have lingering symptoms," Chu said. "There hasn't been sufficient research to understand what causes it or ways to treat it. In the meantime, the first thing we are doing is to try to quantify and describe it."

While the percentage of people reporting long-term symptoms increased with age, they also occurred in younger people, affecting roughly 27 percent of participants ages 18 to 36, 30 percent of those ages 37 to 64, and 43 percent of those 65 and older.

Researchers said the study's findings should serve as a cautionary tale for younger and healthy adults who may not think they are susceptible to complications.

"What's clear is that you can do well initially, but then over time develop symptoms that are quite crippling in terms of fatigue," Chu said.

Watch the study's lead researchers discuss their findings below: