Health experts are not sure exactly what causes long COVID. Some theories include:

• SARS-CoV-2 virus particles become active again in the body after the initial illness or one or more of the person’s organs is taking longer to recover than the rest
• The immune system becomes overactive, causing inflammation in the body
• The overactive immune system makes antibodies that attack organs and tissues

Long COVID health problems may be due to more than one of these factors. Research is ongoing to find out what causes long COVID, and who is most at risk.

Your risk of developing long COVID may be higher if you:

• Had severe illness with COVID-19
• Required hospitalization or intensive care during COVID-19 infection
• Had other health conditions before COVID-19 infection
• Had inflammation in the heart, lungs, kidneys, brain, or other areas if the body following COVID-19 infection (multisystem inflammatory syndrome)
• Are not vaccinated
• Are an older adult
• Are female

People at high risk for COVID-19 infection because of where they live and work and members of communities who don't have good access to health care may also be at risk for long COVID.

People with mild COVID-19 can also develop long COVID. Some people have developed long COVID and never knew they had a COVID-19 infection.

A person who has symptoms that persist for 4 or more weeks after a case of COVID-19 is said to have long COVID. Long COVID does not affect every person the same way. The symptoms may:

• Continue after your initial illness
• Begin later after you recover
• Go away and then come back
• Improve or get worse with time
• Be some of the same symptoms you had when you had COVID-19
• Be new symptoms

Symptoms of long COVID may last for weeks, months, or longer. Although many people have mild symptoms, long COVID can be disabling for some people.

Common symptoms of long COVID include:

• Fatigue or tiredness that makes it hard to do daily activities
• Fever
• Difficulty breathing or shortness of breath
• Cough
• Changes in smell or taste
• Worsening symptoms after vigorous physical or mental activity

Long COVID can affect different body systems and include other symptoms:

• Brain and nerves -- headache, difficulty thinking or concentrating (sometimes called "brain fog"), sleep problems, dizziness, tingling, numbness
• Mental health -- mood changes, depression, anxiety, post-traumatic stress disorder (PTSD)
• Bones and joints -- joint pain, muscle pain
• Digestive -- stomach pain, diarrhea, constipation, appetite changes
• Heart and blood -- Blood clots, chest pain, palpitations (fast or irregular heartbeat)

Long COVID may affect multiple organs in the body, such as the lungs, kidneys, heart, brain, and skin. People who had severe COVID-19 are more at risk for multi-organ effects. This increases the risk for a person to develop diabetes, heart conditions, or neurological problems compared to people who did not have COVID-19.

Some long COVID symptoms, such as muscle weakness and PTSD may result from having spent a long time in the hospital. These effects can occur from any illness that leads to being in bed for a long time and being on a breathing machine (intubated).

Long COVID symptoms vary a lot and can be hard to figure out and manage. Because of this, people with long COVID can have a hard time getting a proper diagnosis.

There are no specific tests for long COVID. Your health care provider may diagnose you with long COVID based on:

• Your symptoms
• A physical exam
• Your health history, including whether you had COVID-19 before
• Complete blood count (CBC)
• Complete metabolic panel
• Urinalysis
• Liver function tests
• C-reactive protein
• Erythrocyte sedimentation rate (ESR)
• TSH
• Free T4
• Chest x-ray
• Electrocardiogram or cardiac MRI
• Tests for vitamin deficiencies vitamin D and B12
• Test for antibodies to COVID-19 to document your initial infection

Medical tests may be normal despite the presence of symptoms, and this does not rule out a long COVID diagnosis.

There is no specific cure for long COVID. Treatment will depend on your symptoms and may include:

• A progressive exercise program
• Physical therapy
• Occupational therapy
• Speech and language therapy
• Neurological rehabilitation (for cognitive symptoms)
• Pulmonary rehabilitation
• Mental health care
• Medicines to help manage symptoms

You may want to consider joining a clinical trial for long COVID. A clinical trial is a study using people who agree to participate in new tests or treatments. Clinical trials help researchers know whether a new treatment works well and is safe. The National Institutes of Health has created RECOVER: Researching COVID to Enhance Recovery where you can learn more about long COVID clinical trials near you.

For the most up-to-date information on long COVID, visit these websites:

Centers for Disease Control and Prevention: Long COVID basics -- www.cdc.gov/covid/long-term-effects/

Centers for Disease Control and Prevention: CDC science and the public health approach to long COVID -- www.cdc.gov/covid/php/long-covid/

US Department of Health and Human Services: COVID-19 treatment information for patients -- aspr.hhs.gov/COVID-19/treatments/Pages/default.aspx

More information and support for people with long COVID and their families can be found at:

• Long COVID Kids -- www.longcovidkids.org/support-services

COVID-19 is a new disease, so no one knows exactly what the outlook will be for people with post-COVID symptoms. Most people who have symptoms at 4 weeks after a COVID-19 infection will gradually improve. Research is ongoing into how to help people with long COVID overcome the condition.

You should contact your provider if you had COVID-19 and you have ongoing symptoms for 4 weeks or more, or the same or new symptoms return 4 or more weeks after your illness.

Call 911 or the local emergency number if you have:

• Trouble breathing
• Chest pain or pressure
• Confusion or inability to wake up
• Blue or gray lips or face
• Any other symptoms that are severe or concern you

The only way to prevent long COVID is to protect yourself from COVID-19 infection.

• Get an updated COVID-19 vaccine.
• Avoid contact with people who are suspected or confirmed to have COVID-19.
• Get yourself tested if you develop COVID-19 symptoms or come in contact with someone with COVID-19.

Post-COVID; Post-COVID conditions; PCC; Long-haul COVID; Post-acute COVID-19; Post-acute sequelae of SARS CoV-2 infection; PASC; Long-term effects of COVID-19; Chronic COVID

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Centers for Disease Control and Prevention website. Clinical overview of long COVID. www.cdc.gov/covid/hcp/clinical-overview/index.html. Updated July 12, 2024. Accessed July 25, 2024.

Centers for Disease Control and Prevention website. Long COVID basics. www.cdc.gov/covid/long-term-effects/. Updated July 11, 2024. Accessed July 25, 2024.

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National Institutes of Health website. Long COVID. covid19.nih.gov/covid-19-topics/long-covid. Updated September 28, 2023. Accessed March 13, 2024.

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Recover: researching COVID to enhance recovery website. What is long COVID? recovercovid.org/long-covid. Accessed March 6, 2024.

Sierpina VS, Seashore J, Kamprath S, Xie C. Post-acute COVID syndrome. In: Kellerman RD, Rakel DP, Heidelbaugh JJ, Lee EM, eds. Conn's Current Therapy 2024. Philadelphia, PA: Elsevier 2024:681-688.

World Health Organization website. Coronavirus Disease (COVID-19). Post COVID-19 condition. www.who.int/news-room/questions-and-answers/item/coronavirus-disease-(COVID-19)-post-COVID-19-condition. Updated March 28, 2023. Accessed March 6, 2024.

Updated by: Frank D. Brodkey, MD, FCCM, Associate Professor, Section of Pulmonary and Critical Care Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 07/03/2024.