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Long COVID symptoms can emerge months after infection

August 10, 2023
University of California - San Francisco
Long COVID can persist for at least a year after the acute illness has passed, or appear months later, according to the most comprehensive look yet at how symptoms play out over a year.

Long COVID can persist for at least a year after the acute illness has passed, or appear months later, according to the most comprehensive look yet at how symptoms play out over a year.

The multicenter study, a collaboration between UC San Francisco, the Centers for Disease Control and Prevention (CDC) and seven other sites, expands knowledge of post-COVID-19 conditions, describing trends in more detail than previous research and highlighting significant impacts the epidemic has had on the U.S. health care system.

The study appears Aug. 10, 2023, in Morbidity and Mortality Weekly Report (MMWR), a publication of the CDC.

For about 16% of the COVID-positive people in the study, symptoms lasted for at least a year; but for others, they came and went. The study assessed symptoms every three months, enabling researchers to differentiate between symptoms that improve and those that emerge months after the initial infection.

"It was common for symptoms to resolve then re-emerge months later," said lead author Juan Carlos Montoy, MD, PhD, associate professor at UCSF's Department of Emergency Medicine. "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."

Fluctuating Nature of Disease

Long COVID involves a range of symptoms that persist or develop about a month after initial infection. These symptoms are associated with significant morbidity or reduced quality of life.

The study involved 1,741 participants -- two-thirds of them female -- who sought COVID testing at eight major health care systems across the country. Three-quarters tested positive for COVID, but those who tested negative may also have had an infection of some type, since they were experiencing symptoms. These included fatigue, runny nose, headache, sore throat, shortness of breath, chest pain, diarrhea, forgetfulness and difficulty thinking or concentrating.

COVID positive participants were more likely to have symptoms in each of the symptom categories at baseline, but by the end of the year, there was no difference between those who were COVID positive and negative.

"We were surprised to see how similar the patterns were between the COVID positive and COVID negative groups," said Montoy. "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 data came from the CDC's INSPIRE project (Innovative Support for Patients with SARS-CoV-2 Infections Registry), which includes Rush University, Chicago; Thomas Jefferson University, Philadelphia; University of California, Los Angeles; University of Texas Southwestern Medical Center, Dallas; UTHealth Houston, Houston; University of Washington, Seattle; and Yale University, New Haven.

Co-authors: From UCSF, co-authors were James Ford, MD, Robert M. Rodriguez, MD, and Ralph C. Wang, MD. For co-authors from other institutions, please see the paper.

Funding: INSPIRE is a CDC-funded project (Contract 75D30120C08008).

Story Source:

Materials provided by University of California - San Francisco. Original written by Elizabeth Fernandez. Note: Content may be edited for style and length.

Journal Reference:

  1. Juan Carlos C. Montoy, James Ford, Huihui Yu, Michael Gottlieb, Dana Morse, Michelle Santangelo, Kelli N. O’Laughlin, Kevin Schaeffer, Pamela Logan, Kristin Rising, Mandy J. Hill, Lauren E. Wisk, Wafah Salah, Ahamed H. Idris, Ryan M. Huebinger, Erica S. Spatz, Robert M. Rodriguez, Robin E. Klabbers, Kristyn Gatling, Ralph C. Wang, Joann G. Elmore, Samuel A. McDonald, Kari A. Stephens, Robert A. Weinstein, Arjun K. Venkatesh, Sharon Saydah, Zohaib Ahmed, Michael Choi, Antonia Derden, Michael Gottlieb, Diego Guzman, Minna Hassaballa, Ryan Jerger, Marshall Kaadan, Katherine Koo, Geoffrey Yang, Jocelyn Dorney, Jeremiah Kinsman, Shu-Xia Li, Zhenqiu Lin, Imtiaz Ebna Mannan, Senyte Pierce, Xavier Puente, Andrew Ulrich, Zimo Yang, Huihui Yu, Karen Adams, Jill Anderson, Gary Chang, Nikki Gentile, Rachel E. Geyer, Zenoura Maat, Kerry Malone, Graham Nichol, Jasmine Park, Luis Ruiz, Mary Schiffgens, Tracy Stober, Michael Willis, Zihan Zhang, Grace Amadio, Alex Charlton, David Cheng, Dylan Grau, Paavali Hannikainen, Efrat Kean, Morgan Kelly, Jessica Miao, Nicole Renzi, Hailey Shughart, Lindsey Shughart, Carly Shutty, Phillip Watts, Arun Kane, Peter Nikonowicz, Sarah Sapp, David Gallegos, Riley Martin, Chris Chandler, Megan Eguchi, Michelle L’Hommedieu, Raul Moreno, Kate Diaz Roldan, Mireya Arreguin, Virginia Chan, Cecilia Lara Chavez, Robin Kemball, Angela Wong, Melissa Briggs-Hagen, Aron J. Hall, Ian D. Plumb. Prevalence of Symptoms ≤12 Months After Acute Illness, by COVID-19 Testing Status Among Adults — United States, December 2020–March 2023. MMWR. Morbidity and Mortality Weekly Report, 2023; 72 (32): 859 DOI: 10.15585/mmwr.mm7232a2

Cite This Page:

University of California - San Francisco. "Long COVID symptoms can emerge months after infection." ScienceDaily. ScienceDaily, 10 August 2023. <>.
University of California - San Francisco. (2023, August 10). Long COVID symptoms can emerge months after infection. ScienceDaily. Retrieved February 27, 2024 from
University of California - San Francisco. "Long COVID symptoms can emerge months after infection." ScienceDaily. (accessed February 27, 2024).

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