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Long Covid

Reviewed by Psychology Today Staff

What Is Long Covid?

Long Covid is a designation created by patients early in the Covid-19 pandemic who found themselves experiencing a course of illness that was longer and more complex than their initial symptoms or than initial reports of acute respiratory infection suggested.

Most people infected with Covid-19 experience a mild to moderate acute infection; fewer than 10 percent develop hypoxemic pneumonia, while 3 percent develop a critical illness. Evidence indicates that more men than women get acute covid, and most people who get Covid recover completely in weeks.

However, some people experience a protracted bout of illness, relapse after an apparent recovery, or develop totally new symptoms—all now known as long Covid. The condition encompasses such an array of symptoms—persistent fatigue, brain fog, shortness of breath, vomiting and diarrhea, cardiac problems, neurologic anomalies—in a range from mild to debilitating, that no one is sure whether it is one condition or several. All evidence indicates that, around the world, more women than men experience long Covid, and most are middle-aged.

Much is unknown about the nature of the coronavirus and how it behaves in the human body. While it was early described as a respiratory virus, it has also proved to have an affinity for cardiovascular, neural, gastrointestinal, and other tissue, affecting many systems of the body, and sometimes overactivating the immune system. It even affects cholesterol metabolism and has been reported to impair erectile function. At the latest count, more than 200 symptoms have been associated with coronavirus infection, especially long Covid, which ranges from mild to completely debilitating.

Signs and Symptoms

Fever, cognitive sluggishness, dry cough, joint pain, skin rashes, the advent of new allergies, swollen and discolored toes, constipation, and shortness of breath—all have been reported in patients for weeks or months after experiencing acute Covid infection. Extreme fatigue, cognitive dysfunction, and memory loss are among the most common symptoms of long Covid, and they are also the most long-lasting.

Patients with long Covid typically report that their symptoms not only affect multiple organs but wax and wane over weeks and months. Exercise, stress, or any physical or mental exertion (post-exertional malaise, or PEM) can trigger a relapse. Many find that they are unable to maintain the work schedule they had pre-Covid, and a significant number of people report they are unable to work at all. Many healthcare experts believe that a disability crisis affecting millions in the U.S. and globally will follow the pandemic and strain resources for years.

What are the most common symptoms of long Covid?

Many symptoms have been associated with long Covid, and patients typically experience multiple symptoms. The most common are:

• Fatigue

• “Brain fog

• Headache

• Neuropathy

• Sleep problems

• Loss of smell/taste

• Memory disturbances


• Chest pain

• Heart palpitations

• Shortness of breath


• Gastrointestinal disruption

• Difficulty swallowing.

In one survey of more than 3,500 people with long Covid, more than 85 percent experienced systemic problems affecting musculoskeletal, cardiovascular, gastrointestinal, pulmonary, and neuropsychiatric systems. The symptoms patients consistently find most debilitating are fatigue, breathing issues, and cognitive dysfunction. 

When does it develop?

Long Covid is defined by the U.S. Centers for Disease Control and Prevention as the presence of Covid-related symptoms more than four weeks after an acute infection. They may be continuing symptoms, symptoms returning after a remission, or symptoms newly arising.

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Incidence and Prevalence

In mid-April 2022, a meta-analysis of 31 studies published in The Journal of Infectious Diseases revealed that 49 percent of Covid-19 survivors reported persistent symptoms four months after diagnosis. The true prevalence is still unknown.

Starting in June of 2022 , however, the percentage of people in the U.S. experiencing long Covid after a bout of infection began declining, according to data published by the CDC. At that time, more than 3 percent of U.S. adults reported having long Covid, while 7 percent reported ever having the condition.

How common is long Covid?

Rates of long Covid appear to vary around the world. Some studies show that 30 percent of Americans who get Covid experience long Covid. But a massive study—of 4.5 million patients treated at U.S. Veterans Administration hospitals—tallies a rate of 7 percent. Even people with asymptomatic Covid can later manifest long Covid, as can those who previously tested negative on antigen or antibody tests.

What percentage of people get long Covid?

It is not yet clear what the true prevalence of long Covid is because the symptoms are so diffuse and studies so far have employed differing criteria and time frames of observation. Estimates range from 10 percent to more than 60 percent of those who get acute Covid. When WHO offered a definition of the condition in December 2021, it reported that “most people who develop Covid-19 fully recover, but current evidence suggests approximately 10 percent to 20 percent of people experience a variety of mid- and long-term effects after they recover from their initial illness.”

According to subsequent analyses of several databases of Covid patients, including those with mild or asymptomatic acute infection, a post-Covid syndrome reportedly develops on average in 30 percent to 60 percent of patients—mainly women. Fatigue, shortness of breath, cough, and loss of sense of smell are among the most common symptoms. 

In February 2022, an editorial in the journal Nature observed that two years into the pandemic, there had been about 400 million confirmed cases of Covid worldwide and many more undocumented. On the basis of available prevalence rates established, it said, about 100 million people were likely suffering from long Covid.


Because long Covid is such a mysterious condition, with symptoms that may shift in nature and intensity, it is extremely difficult to diagnose definitively. In fact, it is a diagnosis made by exclusion, conferred only after no other causes can be found for the highly variable symptoms.

A history of acute Covid infection—however mild—weeks or months earlier is a key indicator. Not only is there an array of nonspecific symptoms, but most of them could also arise from any number of health problems. Further, many of the symptoms—fatigue, headache, difficulty concentrating—also occur among people who are perfectly well.

It’s the very vagueness of symptoms, and their tendency to wax with exertion of any kind, that is highly suggestive. Timing is an important clue, too: The symptoms arise in the wake of acute Covid infection—although the acute infection may have been so mild or so many months earlier that a connection is not immediately apparent.

How do you know if you have long Covid?

It is sometimes hard to know whether you have long Covid. The common symptoms—fatigue, headache, difficulty concentrating—are generally vague in nature, not specific to any disorder, and frequently occur among people who have no disorder. The vagueness of symptoms combined with their tendency to worsen with exertion should raise suspicion, especially if a Covid infection occurred weeks or months earlier or there is a loss of sense of smell.

What should you do if you think you have it?

There is no definitive test or treatment for long Covid. It is entirely possible to experience long Covid without ever having tested positive for the virus or knowing one was infected. Moreover, the wide variety of symptoms could suggest many other possible causes. Nevertheless, if you have a number of unexplained symptoms more than four weeks after an initial infection, consider the possibility of long Covid and plan to see a medical provider.

Although standard blood and other tests may show no abnormalities, they could indicate the presence of conditions that require treatment. 


It is not yet clear what causes long Covid, and it is possible that a post-infectious condition can arise in more than one way. Most experts believe that long Covid is not itself an infectious disorder.

It may be that, during the acute phase of the infection, the virus causes tissue damage that snowballs and reaches clinical significance later. Scientists in several laboratories around the world have found that pieces of the coronavirus—they’ve been called “coronavirus ghosts”—can linger in the gut (and heart, eyes, and brain) for months after acute infection, continuing to cause organ damage and symptoms arising from that damage.

The viral pieces may also stimulate an ongoing inflammatory response. An acute inflammatory response is one of the body’s natural defenses. But if an inflammatory reaction is prolonged for any reason, it itself becomes tissue-destructive, and inflammatory substances can set off a wide range of symptoms in many parts of the body and brain.

In November 2023, researchers reported that the symptoms of long Covid may arise from a decline in levels of the neurotransmitter serotonin, caused by a persistence of the virus in the gut. Studies of both humans and animals suggests that reservoirs of the virus may linger in the gut, causing inflammation, which in turn prevents absorption of the amino acid tryptophan, the precursor of serotonin.

According to the researchers, "Serotonin activity supports vagus nerve function, among other roles. In the study, serotonin loss was associated with lower nerve activity. Dysfunction in the vagus nerve was linked with characteristic long COVID symptoms such as memory loss and hippocampal dysfunction."

How could autoantibodies contribute to long Covid?

There are many facets of the immune system, and differing patterns of immune dysregulation triggered by the coronavirus could underlie the differing symptoms seen in long Covid. Some researchers contend that the production of autoantibodies—antibodies that mistakenly attack body tissue and produce conditions such as rheumatoid arthritis and lupus—is a hallmark of long Covid.

How could existing immune cells be a culprit?

The virus may infiltrate and “hide out” in immune cells in many body systems. And then reactivate. Or the hidden virus could trigger an immune response that then causes inflammation and damage to many parts of the body. Or it could reactivate other dormant viruses from long-ago infections, notably the Epstein-Barr virus, which causes mononucleosis.

The virus is also known to infect the lining of blood vessels and could set off a cascade of events accounting for the widespread nature of symptoms. There’s evidence the virus alters the epithelial cells lining blood vessels and affects how they function, triggering tiny blood clots anywhere in the body and even disturbing cholesterol balance. The formation of blood clots can disrupt the blood supply to various organs, including to the heart.

Under what conditions coronavirus infects or persists in body tissue, stimulates an overzealous inflammatory immune response, triggers tiny blood clots in various organs, or otherwise generates a distinctive chronic disorder is under active investigation by networks of researchers around the world. 


Because no one knows exactly what long Covid is—and it appears to be an assortment of conditions, not one—the best treatments currently available address specific symptoms. For example, a behavioral treatment, olfactory training, is often prescribed for those who have lost their sense of smell. It not only restores olfactory capability but is thought to bolster other functions of the brain. Physical therapy may be prescribed for those who have dizziness, shortness of breath, fatigue, or muscle weakness. The current goal of most treatments is to restore function and return patients to a high quality of life.

Increasingly, major medical institutions are opening treatment centers that specifically focus on people with long Covid. Most such centers pull together specialists from multiple disciplines to address problems holistically.

Is there a cure for long Covid?

There is no cure for long Covid because physicians are not sure what causes long Covid. There are, however, treatments for some of the symptoms. One of the most important treatments for long Covid is targeted at those who have lost a sense of smell. Studies show that one effect of Covid is to downregulate olfactory receptors. The treatment is a behavioral program of olfactory training, involving exposure to sets of odors twice a day and connecting the smell with a memory of that odor. A dampened sense of smell seems to be linked to lasting changes to the brain; it is thought that the lack of sensory input causes the brain's olfactory center to atrophy. The treatment, clinicians say, is important because beefing up the smell areas of the brain also affects the brain centers of memory and emotion regulation, to which they are connected.

Clinicians experienced in treating long Covid patients also emphasize the importance of maintaining blood volume through salt intake and adequate hydration. In addition, they recommend engaging in movement, starting with recumbent exercise.

Can it ever go away on its own?

The course of long Covid can be highly variable. As physicians gain experience with long Covid, they note that it generally tends to resolve slowly over time. Fatigue on exertion seems to be one of the last symptoms to resolve.


With so little known about the precise causes of long Covid, it’s premature to provide directives for preventing the condition. Still, some information is emerging.

The best-known prevention for long Covid is thought to be a vaccination against Covid. Several studies show that vaccination lowers the risk of long Covid, although by how much is not clear—it varies from 15 percent to 50 percent, depending on the study. Some researchers contend that the risk of long Covid is mitigated primarily because vaccination curbs the risk of acute Covid infection in the first place.

But there’s also evidence that vaccination reduces the likelihood of lung problems and minimizes the risk of blood-clotting problems, sources of extended damage. Further, reports suggest that vaccination prevents the production of autoantibodies in response to Covid infection, tissue-destroying immune cells implicated as a possible cause of long Covid.

It may be that antiviral vaccination in general—even against the common flu—may act as a preventive, at least for a period of unknown duration, because it provides a general boost to the immune defense system. It is known that some long Covid patients experience improvement in their symptoms after getting a dose of the coronavirus vaccine. The shot may be fortifying an immune system that failed to mount an adequate response to coronavirus infection, paving the way for long Covid.

Suboptimal hydration, especially of the nose and throat, appears to be an important risk factor for acute Covid infection. What’s more, it worsens symptoms that do occur. Researchers find that inadequate hydration enables the coronavirus to travel deep into the lungs and damage small airways. In addition, dehydration thickens lung secretions, making breathing difficult and impeding blood oxygenation. Tissue damage resulting from inadequate tissue oxygenation is thought to be a source of the diverse health problems linked to long Covid.

Uncertainty about the degree of protection against long Covid provided by vaccines, researchers and clinicians say, highlights the importance of basic infection-containment measures such as mask-wearing and social distancing. Such measures are especially important for those with a compromised immune system.


Callard, F., & Perego, E. (2021). How and why patients made Long Covid. Social science & medicine (1982), 268, 113426.

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