Studies show that symptoms evolve over time, with many patients experiencing headaches and fatigue. New data from a national study recently published in the journal Open Forum on Infectious Diseases suggests that Long-COVID is not a single condition and should not be treated in isolation.

A recent national study shows that long-term COVID-19 is not a single condition but evolves over time. The study, which involved nearly 6,000 participants, highlighted different symptom categories and emphasized the importance of tailoring treatment to symptom presentation.

The study examined COVID-19 patients' ongoing symptoms three and six months after diagnosis. Of the 5,963 people who participated in the study, 4,504 tested positive for COVID-19, while 1,459 tested negative. Many of the participants (2,000 in total) were from King County and attended Washington University School of Medicine.

The four main symptom categories for people who test positive for COVID-19 include:

Mild symptoms (72% of cases)

Fatigue, headache, and muscle/joint pain (17% of cases)

Fatigue, headache, muscle/joint pain with loss of taste and smell (5% of cases)

Symptoms across multiple systems (6% of cases)

The study has clinical implications because it shows how the long-term symptoms of the virus change its appearance over time, said senior author Kari Stephens, research associate and chief of the Department of Family Medicine. Professor in the Department of Biomedical Informatics and Medical Education at Washington University School of Medicine.

Most long-term COVID-19 studies have focused on individual symptoms, without considering clusters or patterns of symptoms. Many don't have a control group and focus only on data captured by providers during clinic visits, rather than directly from patients, she said.

"This study also provides health care providers with information about the long-term consequences of COVID-19 in patients over time," she said. "It will help us understand how we need to treat long-term COVID-19 over time, in a very specific way based on each patient's symptom profile."

What's unique about this study is that people were able to report symptoms directly, regardless of whether they received medical care.

"While it is becoming increasingly clear that long-term COVID-19 is not a single condition, having data showing several distinct, symptom-defining phenotypes is an important step toward developing evidence-driven approaches to treat the millions of people who continue to experience lingering symptoms," said lead author Michael Gottlieb, vice chair of emergency medicine research at Rush University Medical Center.

Overall, Stephens added, the study will help determine funding and policy support for long-term COVID-19 programs: "We don't want to forget about long-term COVID-19 as we all return to 'normal'. New long-term COVID-19 cases are happening every day."

Currently, the CDC estimates that 11% of people infected with COVID-19 are experiencing long-term COVID symptoms.