A new study published today reveals “the true burden of disease” – COVID can stay hidden for almost a year and its symptoms can reappear months after initial infection.

Researchers have uncovered that long-term effects of COVID, often referred to as “long COVID,” can persist for a year following the acute phase of the disease or even emerge several months afterward. This latest study offers a more thorough exploration of the COVID symptom trajectory over time.

This joint research, conducted by UC San Francisco, the CDC, and seven additional institutions, delves deeper into post-COVID conditions, providing insights into the pattern of symptoms more intricately than prior studies. The findings also underscore the considerable strain the pandemic has placed on the U.S. healthcare infrastructure.

The research findings were published today in the CDC’s Morbidity and Mortality Weekly Report (MMWR).

In the study, approximately 16% of the COVID-positive participants experienced symptoms for at least a year, while others faced fluctuating symptoms. By examining symptoms at three-month intervals, the scientists were able to distinguish between symptoms that improved and those that surfaced months after the initial infection.

Juan Carlos Montoy, MD, PhD, the study’s lead investigator from UCSF’s Department of Emergency Medicine, noted, “It was common for symptoms to resolve then re-emerge months later.

“A lot of prior research has focused on symptoms at one or two points in time, but we were able to describe symptom trajectory with greater clarity and nuance. It suggests that measurements at a single point in time could underestimate or mischaracterizes the true burden of disease.” 

Understanding Long COVID Dynamics

Long COVID includes a spectrum of symptoms that continue or manifest roughly a month post-initial infection, often leading to considerable health issues and decreased life quality.

The research encompassed 1,741 subjects, predominantly female, who sought COVID testing at eight leading healthcare facilities nationwide. While three-quarters tested positive for COVID, those who tested negative might also have had some infection, as they displayed symptoms like fatigue, headaches, shortness of breath, chest pain, and difficulty thinking, among others.

At the beginning of the study, COVID-positive participants were more prone to symptoms, but by the end of the year, the difference between the COVID-positive and negative groups vanished.

Highlighting this observation, Montoy remarked, “We were surprised to see how similar the patterns were between the COVID-positive and COVID-negative groups.

“It shows that the burden after COVID may be high, but it might also be high for other non-COVID illnesses. We have a lot to learn about post-illness processes for COVID and other conditions.”  

The gathered data stems from the CDC’s INSPIRE initiative, which collaborates with institutions such as Rush University, Chicago; University of California, Los Angeles; and Yale University, New Haven, among others.

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