Most Long COVID Cases Started With Mild Symptoms: Study

Ralph Ellis

January 06, 2023

Editor's note: Find the latest long COVID news and guidance in Medscape's Long COVID Resource Center.

Just because you start out with a mild case of COVID-19 doesn’t mean you won’t develop long COVID, researchers say.

"We found that a staggering 90% of people living with long COVID initially experienced only mild illness with COVID-19," researchers Sarah Wulf Hanson, PhD, MPH, and Theo Vos, MD, PhD, both of the University of Washington, said in an article about their research in The Conversation.

"After developing long COVID, however, the typical person experienced symptoms including fatigue, shortness of breath and cognitive problems such as brain fog -- or a combination of these — that affected daily functioning. These symptoms had an impact on health as severe as the long-term effects of traumatic brain injury."

Their study was published in October in the  Journal of the American Medical Association.  

The research team looked at data from 54 studies on 1.2 million people in 22 nations who reported having COVID symptoms. They defined long COVID as a continuation of symptoms 3 months after initial infection, with those symptoms lasting at least 2 months. 

Women had twice the risk of men of developing long COVID and four times the risk of children, the study found, and 1 in 7  people infected still had symptoms a year later. People who were hospitalized with COVID were more likely to develop long COVID, but most COVID patients were not hospitalized.

Most of the people in the study were infected before Omicron became the dominant strain. It’s not clear if Omicron infections will result in as much long COVID, but initial research shows lower risk, the researchers wrote. 

Long COVID has an immense impact on people’s lives and their ability to work, Hanson and Vos wrote, noting that researchers should make finding effective and affordable treatments for long COVID a priority.


Journal of the American Medical Association. "Estimated Global Proportions of Individuals With Persistent Fatigue, Cognitive, and Respiratory Symptom Clusters Following Symptomatic COVID-19 in 2020 and 2021."

The Conversation: "Long COVID stemmed from mild cases of COVID-19 in most people, according to a new multicountry study."


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