Long COVID, also known as Post-COVID Conditions (PCC), refers to the wide range of symptoms and conditions that some people experience four or more weeks after an initial infection by SARS-CoV-2, the virus that causes COVID-19. The symptoms and conditions, which may last for weeks, months, or years, can be persistent (meaning they developed during an acute COVID-19 illness and haven’t gone away), recurrent (meaning they may go away after the initial illness then return), or new (meaning they were not present initially but developed later).

Symptoms of Long COVID can range in severity from mild to debilitating. Some people report that Long COVID symptoms prevent them from returning to work or school, and others have difficulties performing everyday chores or even walking short distances.

Long COVID most often occurs in people who had severe COVID-19 illness, but it is not restricted to those who were critically ill or hospitalized. People with mild disease and even those who did not develop symptoms can also be affected. In fact, most people with Long COVID had mild acute COVID-19. This is because many more people have mild COVID-19 than severe COVID-19, so even if a small percentage of them develop Long COVID, they nevertheless account for the majority of Long COVID cases. Adults and children can both be affected, though Long COVID appears to be more common in adults. Researchers do not yet know how common the condition is, but studies have estimated that it occurs in 5% to 30% of people with COVID-19.

In addition to PCC, Long COVID goes by many other names, including long-haul COVID, post-acute sequelae of COVID-19 (PASC), long-term effects of COVID-19, and chronic COVID, among others.

Long COVID can affect anyone, including children, and it can develop in people who had asymptomatic, mild, or severe COVID-19. Some people, however, are at increased risk, including:

• People who have had severe COVID-19, in particular those who required hospitalization or intensive care
• People with underlying health conditions such as diabetes, asthma, or obesity
• People who have not gotten a COVID-19 vaccine
• People who had multisystem inflammatory syndrome (known as MIS-C in children and MIS-A in adults) during or after COVID-19

Women and older people may also be at increased risk for Long COVID as well as those who have repeat SARS-CoV-2 infections. According to a Centers for Disease Control and Prevention (CDC) National Center for Health Statistics data brief, in the U.S., adults between 35 and 49 years of age are the age group most likely to have had Long COVID previously or to currently have Long COVID.

Some variants of the coronavirus that causes COVID-19 have been more frequently linked to Long COVID than others.

While the causes of Long COVID are not yet known—and research is ongoing—researchers and clinicians have proposed several theories, including:

• Remaining virus. This theory suggests that after the immune system eliminates the coronavirus, some remnants survive in one or more organs, and it continues to stimulate an immune response. The immune response may damage tissues and result in chronic inflammation, leading to Long COVID symptoms.
• Reactivation of latent viruses. Some viruses in the herpesvirus family, such as the Epstein-Barr virus (the virus that causes mononucleosis), that infected a person in the past may remain in the body in an inactive, or dormant, state. There is evidence that in people with Long COVID, these inactive viruses reactivate, which may cause Long COVID symptoms.
• Autoimmune response. According to this theory, the immune system produces antibodies that target and attack a person’s own organs and tissues.
• Organ damage. This theory holds that the symptoms of Long COVID are due to damage to organs and/or tissues caused by the body’s immune response to SARS-CoV-2 infection.

Long COVID may be caused by a combination of these and other factors. Investigations are still underway to better understand Long COVID, and much research is still necessary.

COVID-19 can affect the function of multiple organs in the body, including the lungs, heart, brain, kidneys, and liver. Because of this, Long COVID is associated with a broad range of symptoms, including respiratory, neurological, cardiac, and psychological problems, among others.

People with Long COVID may have a number of symptoms that last for weeks, months, or years after infection with the virus that causes COVID-19.

Symptoms of Long COVID may include:

• Fatigue, feeling tired
• Weakness
• Brain fog (problems concentrating or thinking)
• Headaches
• Tremor
• Rapid or pounding heartbeat, feeling of skipped heartbeats (palpitations)
• Dizziness upon standing
• Symptoms that worsen after physical or mental activity (known as post-exertional malaise, PEM)
• Gastrointestinal symptoms including stomach pain, diarrhea, and/or constipation
• Loss of or change in smell and/or taste
• Thirst (for instance, dry mouth)
• Cough
• Changes in comfort or capacity for sex and/or desire for sex
• Chest pain, tightness, or pressure
• Hearing problems, including hearing loss or ringing in the ears (tinnitus)
• Shortness of breath
• Muscle and/or joint pain
• Back pain
• Sleep apnea
• Fever, sweats, and/or chills
• Hair loss
• Sleep problems, including insomnia
• Bladder problems, including difficulty urinating or incontinence
• Vision problems, such as blurry vision, sensitivity to light, floaters, flashing lights, or difficulty reading or focusing eyes
• Depression
• Anxiety
• Swelling of the legs
• Problems with teeth
• Foot pain
• Skin rash
• Abnormal movements
• Skin color changes (for instance, skin that is red, white, or purple)
• Changes in menstrual cycle

Some people may experience only one of these (or other) symptoms, while others may have two or more. Symptoms can vary greatly from one person to the next.

Some people report that Long COVID symptoms prevent them from returning to work or school, and some with Long COVID have difficulties performing everyday chores or even walking short distances.

COVID-19 can damage multiple organs throughout the body, including the brain, heart, lungs, liver, and kidneys, among others. When this happens, it can increase the risk of the development of new medical conditions, including:

• Diabetes
• Kidney disease
• Heart conditions
• Neurological conditions
• Blood clots
• Postural orthostatic tachycardia syndrome (POTS), a condition in which the heart beats faster when standing up from a lying down position and can cause lightheadedness and fainting)

There is no single test to diagnose Long COVID. Doctors diagnose it, in large part, based on a patient’s history of COVID-19 and by ruling out other possible causes of their symptoms.

The doctor will ask whether you tested positive for COVID-19, when symptoms began and their severity, and which symptoms you have experienced since the initial infection. The doctor may also ask about underlying medical conditions.

After collecting a medical history, the doctor will conduct a physical exam. The exam will involve a routine assessment of blood pressure, heart rate, temperature, pulse oximetry, and breathing. Depending on your symptoms, it may also involve physical, cognitive, and psychological testing. Physical tests may include a 6-minute walking test and/or a one-minute sit-to-stand test. Cognitive assessment may involve short tests to evaluate memory, language ability, reasoning, and other cognitive skills. With psychological testing, you may need to complete a screening questionnaire.

Depending on your symptoms, the doctor may order specific diagnostic tests. If you are experiencing respiratory symptoms, for instance, a chest X-ray and pulmonary function tests may be required. An electrocardiogram (known as an ECG or EKG), a painless test that measures heart activity, may be necessary if you have cardiac symptoms. In some cases, the doctor will order bloodwork.

Because people with Long COVID can experience a wide range of symptoms, there is no single treatment for the condition. People with Long COVID should work with a health care provider to develop a personalized treatment plan to manage their symptoms and optimize their quality of life.

For patients with multiple symptoms, treatment may involve specialists in cardiology, pulmonology, neurology, psychiatry, rehabilitation, and/or other relevant fields of medicine. Often, a primary care doctor or other health care provider can manage Long COVID treatment in consultation with specialists.

Below, by symptom, are treatments and therapies that may help people with Long COVID:

• Fatigue. Patients may be taught strategies for “Pacing, Planning, Prioritizing, and Positioning” activities, sometimes known as the “4 Ps.” They may also be advised to participate in activities they can do based on their level of fatigue. Over time, patients may gradually increase the amount and/or intensity of activity, but if symptoms worsen with the increased activity level, the patient should reduce activity to a tolerable level.
• Respiratory symptoms. Treatment for patients with shortness of breath may involve breathing exercises, the use of supplemental oxygen, and pulmonary rehabilitation, a medically guided program in which patients perform exercises and learn breathing techniques. In some cases, medications such as corticosteroids may be prescribed. Patients may need to use a pulse oximeter to monitor blood oxygen saturation levels. (If blood oxygen saturation levels fall below 92%, they should seek medical attention.) If respiratory symptoms do not improve, patients may be referred to a pulmonologist.
  
  For patients with a persistent cough, over-the-counter cough suppressants may help reduce symptoms. In some cases, inhalers (bronchodilators or glucocorticoids) or other medications may be prescribed to manage cough symptoms.
  
  Persistent chest discomfort or pain may be treated with nonsteroidal anti-inflammatory drugs (NSAIDs). People with chest tightness may benefit from the use of an inhaled bronchodilator medication (given via an inhaler). If chest pain is caused by a heart problem caused by COVID-19, such as myocarditis, patients may be referred to a cardiovascular specialist for evaluation and treatment.
• Cardiac symptoms. Patients with cardiac symptoms may be referred to a cardiovascular specialist for cardiac symptoms, such as rapid heart rate or chest pain. Treatment may involve cardiac rehabilitation. Medications may also be used to control specific symptoms.
• Neurological symptoms. For patients with memory impairment, treatment might involve neurologic rehabilitation. Some people may find the use of memory aids, such as calendars and planners, useful in managing tasks and schedules. Patients may be referred to a neurologist.
• Psychological symptoms. Treatment may involve counseling, support groups, and medications to manage depression, anxiety, or other conditions.
• Smell and taste symptoms. Patients who have a reduced or lost sense of smell and/or taste may also undertake olfactory training, a therapy in which they regularly sniff various odors for a set period (usually several weeks) with the aim of restoring their sense of smell. If symptoms do not resolve, patients may be referred to an ear, nose, and throat (ENT) specialist.
• Insomnia and sleep symptoms. Treatment may involve counseling on sleep hygiene, including keeping a consistent sleep schedule, avoiding naps, getting adequate exercise, limiting caffeine consumption, and avoiding alcohol and nicotine around bedtime. Patients may also be taught relaxation techniques.

Patients who have symptoms related to kidney, liver, or endocrine function—as well as those related to dermatology and gastrointestinal issues—are usually referred to the appropriate specialist.

Treatment may also involve physical therapy, occupational therapy, vocational therapy, and/or speech and language therapy.

Because COVID-19 is a new disease, the long-term outlook for people with Long COVID is not fully known. For many people with Long COVID, symptoms resolve on their own within three months after the onset of their initial COVID-19 illness. For others, however, symptoms can continue well beyond three months and last for years. For those with multiple symptoms, some may resolve while others persist.

Treatments and therapies for Long COVID can help manage symptoms, improve quality of life, and help people gradually rehabilitate. Researchers continue to learn more about Long COVID, including ways to treat it and help people recover from it.

The Yale New Haven Long COVID Multidisciplinary Care Center evaluates people experiencing Long COVID symptoms and works closely with an array of specialists, including cardiologists, neurologists, pulmonologists, and rheumatologists, to find the best treatments for them.

“We also created the Yale Center of Infection & Immunity to unravel disease pathogenesis of Long COVID and its related post-acute infection diseases,” says Akiko Iwasaki, PhD, Sterling Professor of Immunobiology and Molecular, Cellular, and Developmental Biology at Yale University and director of Yale’s Center of Infection & Immunity. “I am hopeful that our multi-pronged approaches to biological analysis will lead to insights useful for diagnosis and treatment. Our Paxlovid clinical trial will also probe the role of persistent virus in causing long COVID.”