The emerging topic of “long COVID” is defined by a range of symptoms that can last weeks or months, even after the COVID-19 virus has been cleared from the body.
Long COVID can affect anyone, regardless of the severity of their COVID-19 infection. However, there may be some groups of people who are more likely to show long-term symptoms.
The cause of long COVID remains unknown, but researchers have developed potential theories as to why we’re seeing this condition.
Each person’s road to recovery is unique, so management of long COVID symptoms can vary from person to person.
In the second year of the COVID-19 pandemic, long COVID, also known as “post-acute COVID,” is emerging as a prevalent syndrome. It is characterized by an array of symptoms that persist weeks or months following COVID-19 infection. Long COVID can happen to anyone, whether their infection was mild or severe. Treatment of long COVID is focused on symptom management and monitoring for potential complications.
In this article, we will look at what long COVID is, who is getting these prolonged symptoms and why, potential complications, and how long COVID is managed.
COVID-19 is an infection caused by a coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Coronaviruses are a large family of viruses that infect a wide variety of mammals, including humans.
Some of these viruses are common and cause mild infections (such as the common cold), while others are rare and can cause severe and sometimes fatal diseases. The most well-known coronaviruses are SARS-CoV (severe acute respiratory syndrome coronavirus, which caused a pandemic in 2002–2003) and MERS-CoV (Middle East respiratory syndrome coronavirus, which has been causing severe respiratory disease in humans since 2012). (Source)
COVID-19 was first identified in late 2019, and we have developed extensive knowledge regarding the virus and its disease. We have established how the disease progresses upon infection, allowing us to recognize acute symptoms and the immediate effects of COVID-19. Now this leads to the next growing question: How does infection with COVID-19 affect an individual in the long-term?
Most people recover from COVID-19 symptoms within 2 weeks, but some may experience long-term symptoms. There is new evidence emerging regarding this condition, commonly known as long COVID. Other terminology you may see regarding this condition includes:
Long COVID can happen to anyone, regardless of the severity of their COVID-19 infection. Symptoms may persist after infection, or may appear for the first time after the infection has cleared. Moreover, there have been multiple studies that have determined that 50%–80% of patients continue to have symptoms 3 months after the infection, even when lab tests detect no virus in the body. (Source, Source)
There is no definite agreement yet as to when we can say someone has developed long COVID. Definitions include:
Patients with long COVID are typically termed “long haulers.” Currently, we don’t have enough evidence to say exactly who is most susceptible to becoming a long hauler. Sometimes patients who only had mild COVID-19 symptoms continue to have long-term effects, whereas some patients who were severely ill return to normal health 2 months later. (Source)
While we can’t say yet who is most likely to develop long COVID symptoms, certain trends have been identified. Current studies suggest risk is highest among:
Further studies are needed to confirm whether these trends are consistently seen.
There have been many symptoms associated with long COVID. Some symptoms develop during infection and persist afterward, and some appear weeks after infection.
Long COVID signs and symptoms include:
These symptoms can appear in various combinations for different individuals who have had COVID-19.
It is still not known why these long COVID symptoms arise. As time goes on, we will be able to monitor COVID-19 patients for longer periods and study the long-term symptoms more effectively. For now, there have been a few theories developed as to why long COVID is happening.
As COVID-19 is a respiratory infection, we know that it mainly targets the lungs. For some, there may be no damage during the time of infection, but others may have more severe outcomes. Some people may experience more severe coughs and breathlessness.
In the most critical cases, patients can develop COVID-19-associated pneumonia or an acute respiratory distress syndrome requiring intensive medical intervention, often including mechanical ventilation. The lungs, along with other organs, may be further damaged by serious systemic complications such as sepsis, or by other pathogens that attack while the immune system is stressed. We don’t yet know how long lasting this damage will be. (Source, Source)
Another theory for the possible cause of long COVID is that the COVID-19 virus may affect the autonomic nervous system, which is responsible for controlling many of the unconscious functions of your body, such as your heart rate and blood pressure.
The theory is that COVID-19 causes autonomic dysfunction that disrupts the body’s ability to adjust heart rate and blood pressure when a person stands or sits up. This causes what are known as orthostatic intolerance syndromes, in which the inability to coordinate autonomic functions causes tachycardia (fast heart rate), palpitations, breathlessness, and chest pain when a person gets up from sitting or lying.
Long COVID has been compared to ME/CFS, a disabling condition that has no clearly identified cause but may have an autoimmune origin or be triggered by a viral infection. Long COVID, ME/CFS, and other post-infectious fatigue syndromes are well documented but not well understood.
Many symptoms of long COVID are similar to those of ME/CFS. The symptoms considered in a diagnosis of ME/CFS include:
In an opinion piece published in Frontiers in Medicine, the authors discuss the possibility that a given percentage of those infected with COVID-19 will develop ME/CFS or a similar post-infectious fatigue syndrome. They conclude ongoing monitoring for these conditions is needed. (Source)
As of right now, ME/CFS is not on the list of predisposing medical conditions for COVID-19, however people with this illness may consider taking extra precautions to lower their risk of COVID-19 infection and subsequent long COVID. (Source)
Although this is an emerging field of research, another possible cause of long COVID may be a pre-existing autoimmune disease. Autoimmune conditions are abnormal immune responses in which antibodies are directed toward healthy human tissue. These self-attacking antibodies are termed “autoantibodies.” (Source)
The evidence is not yet conclusive, but the presence of autoantibodies at the time of infection may pose a risk for developing long COVID. The already existing autoantibodies in the body may be triggered by COVID-19 and cause longer-term damage to the body even after the virus has been cleared. (Source)
Long COVID may be diagnosed based on symptoms that persist for weeks or months (or even years — we don’t know yet) after infection. The first step is to try to determine whether symptoms are due to long COVID or to some other disease process.
Diagnostic tests can be useful to rule out other causes of symptoms that are associated with long COVID. These may include full evaluation of COVID-19 symptoms as well as antibody or chest imaging tests. (Source)
If you had a symptomatic case of COVID-19 and a positive virus test at the time of infection, your health care provider will compare the symptoms you had initially with your current symptoms. To do this, they may check your heart rate and blood pressure, temperature, and your overall lung function.
However, not everyone with long COVID will have had a positive test that confirmed SARS-CoV-2, especially early on in the pandemic when tests weren’t widely available. Also, some who were infected with COVID-19 remained asymptomatic. They may develop long COVID symptoms without even knowing they were infected with SARS-CoV-2. (Source)
Antibody tests check your blood for antibodies to the virus that causes COVID-19. Even if you have never had symptoms of COVID-19, you may still test positive for the viral antibodies, meaning you had an asymptomatic infection. Antibody tests aren’t accurate until at least 1 to 3 weeks after infection, as it takes that long for COVID-19 antibodies to be produced. (Source)
Common chest imaging tests include chest X-rays, computed tomography (CT), and lung ultrasound. Since COVID-19 is a respiratory disease, there may have been damage to the lungs during the time of infection. These chest imaging tests may reveal long-term lung damage that could be indicative of a past infection with the COVID-19 virus. Each test examines the chest region of the body, but they do it in different ways.
One study examined accuracy among the three types of chest imaging tests to see which was best at diagnosing COVID-19. A review of 51 research studies concluded there is limited evidence to directly compare the three for accuracy and reliability.
The researchers rated the three tests on the basis of sensitivity, or how often they correctly determined the patient did have COVID-19, and specificity, or how often they correctly determined the patient did not have COVID-19. They found:
This information could potentially be useful for the exclusion of long COVID in patients with negative imaging tests. However, the research done for chest imaging tests in the context of long COVID is limited and inconclusive. This is a result of few studies focusing on lung health after COVID-19 infection. (Source)
In a study published in Annals of the American Thoracic Society, investigators tackled this knowledge gap by examining post-COVID-19 chest X-rays and CT scans in over 150 patients who had recovered from the infection. They found few cases of lung scarring, known as fibrosis, in which development of thick, hard tissue follows damage or injury.
Only about 4% of patients in this study showed evidence of lung scarring on their CT scans. This may indicate COVID-19 does not cause a significant amount of fibrosis following infection of the lungs, making imaging tests of limited value in diagnosing previous infection with COVID-19. However, there is very limited research on this topic and further study is needed to determine exactly how long COVID could appear on chest imaging tests. (Source)
Since there is still no concrete diagnostic test for long COVID, it may be beneficial to run tests to rule out some of the many other possible causes of symptoms.
An alternative diagnosis could potentially be obtained through testing for abnormalities in biomarkers and organ function, including:
Current research has shown that long COVID may be linked with long-term cardiovascular effects, multisystem inflammatory syndrome (MIS), and development of autoantibodies linked to various autoimmune diseases. These complications may most affect those with ongoing disabilities. However, much is still unknown regarding the prevalence of these complications and whether or not they are actually linked to long COVID.
COVID-19 is primarily a respiratory infection. However, the angiotensin-converting enzyme 2, or ACE2, receptors the virus binds to in the respiratory tract are also found on the heart. Research is inconclusive as to whether the heart is targeted directly via ACE2 receptors or whether it is affected as part of widespread organ inflammation.
It does seem clear that those with pre-existing cardiovascular diseases that stress the heart and limit its oxygen supply are in the greatest danger of severe complications. Recent evidence shows there should be a focus on long COVID patients who are at particular risk for heart complications, such as athletes at risk for exercise-induced arrhythmias and anyone with residual cardiopulmonary symptoms. (Source, Source)
Multisystem inflammatory syndrome can occur after COVID-19, especially in children and adolescents. While these patients tend to have mild or even asymptomatic COVID infections, some go on to develop MIS after, rather than during, acute infection.
Multisystem inflammatory syndrome in children after COVID-19 infection has come to be known as MIS-C. There is still no universal definition of this syndrome or agreement on its symptoms or cause, but the clinical features of MIS-C are similar to those of other well known inflammatory syndromes in children, including Kawasaki disease, Kawasaki disease shock syndrome, and toxic shock syndrome. Most cases of MIS-C are managed in the same way as Kawasaki disease. (Source)
The increasing knowledge of MIS-C in children and young people is allowing for a better characterization of the inflammatory disease. In particular, the CDC has been monitoring MIS-C cases since May 2020 and as of May 3, 2021, has identified 3,742 cases with 35 deaths. However, the disorder still needs a clear clinical and pathophysiological description. (Source)
MIS can also affect adults as a complication of COVID-19 infection. The exact presentation of MIS in adults is still being established, but should still be considered by clinicians when treating adult long COVID patients.
Autoimmune conditions develop when the immune system loses the ability to tell the difference between its own cells and foreign cells, and begins to produce autoantibodies against its own healthy cells. Consequently, this leads to inflammation and a variety of autoimmune diseases. (Source)
Research has shown that infection with COVID-19 may lead to the development of autoantibodies seen in various autoimmune diseases, such as rheumatoid arthritis and lupus. In a study published this year in Nature, researchers reported they identified a wide variety of autoantibodies in COVID-19 patients.
Some of these autoantibodies attacked the virus, but others interfered with immune function and seemed to be responsible for more severe illness. They also found autoantibodies that reacted with various organ systems, including the lungs, central nervous system, and gastrointestinal tract. This suggests patients may develop autoantibodies during infection that then contribute to chronic conditions associated with long COVID. (Source)
Long COVID treatment is focused on management of symptoms, and depends on how severe the symptoms are. Those with serious post-COVID medical conditions such as abnormal blood clotting may require ongoing medical care.
Many, though, have long COVID symptoms that are best managed with holistic approaches including diet, exercise, and medication.
Some suggestions for managing long COVID symptoms include:
These are just some of the ways symptoms can be managed. Each person’s road to recovery is unique. Overall, it is important that you pay attention to your general health and continue to monitor your symptoms. Seek medical advice if your symptoms begin to worsen or if you have any concern regarding your symptoms.
With the rollout of COVID vaccines, we are continuing to learn the role vaccines play among those with long COVID. Current small studies and informal surveys have shown that some people have reported relief of long COVID symptoms following the vaccine.
For example, a small study done in the UK (not yet peer reviewed — meaning this is new research that still needs to be evaluated) found that 23% of long COVID patients reported improvement in their symptoms following vaccination. In comparison, they found that only 15% of unvaccinated long COVID patients reported improvement in their symptoms over the same time frame. Importantly, they concluded that taking the vaccine was not associated with any worsening of long COVID symptoms. (Source)
It is key to note that larger and more formal studies are needed to examine the effects of the vaccine. All in all, if you have long COVID symptoms, you should still get vaccinated!
We are only at the start of the long COVID journey. As we move forward, researchers may uncover more about the effects of long COVID, such as whether it is associated with a predisposition to other conditions later in life. While the exact cause of long COVID is unknown, there are various theories being proposed that may explain symptoms that follow infection with the COVID-19 virus. As further research is done on long COVID, we will hopefully develop a better understanding of this condition and how it progresses.