Post-Acute Covid and Long Covid

People affected by post-acute or long covid (July 2020)

Updated: January 2022
Published: August 2020
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Post-acute covid and long covid: Frequency, causes and treatment options.


A) Frequency; B) Symptoms; C) Causes; D) Diagnosis; E) Treatment; F) Prevention & vaccination; G) Children; H) Post-viral syndrome; J) Myocarditis; K) Media reporting

Note: Patients are asked to consult a doctor.

General considerations

‘Long covid’ has been both unnecessarily exaggerated and unfairly downplayed or denied. Overall, long covid is a clinical reality whose total public health impact is still difficult to predict. It is important to understand that long covid can affect even young people at low risk of severe acute covid as well as vaccinated people.

From a medical perspective, it should be distinguished between:

  1. Post-acute covid (i.e. prolonged recovery phase, up to 4 or 6 months)
  2. Long covid (chronic symptoms without improvement, beyond 6 months)

as well as between:

  1. Symptoms specific to covid (e.g. loss of taste or smell, shortness of breath)
  2. Non-specific (post-viral) symptoms (e.g. general fatigue, digestive problems)

For instance, full recovery from viral pneumonia (even if ‘mild’) and full regeneration of the sense of taste or smell may take several weeks or months (see below).

A. Frequency

Approximately 10% of people with symptomatic SARS-CoV-2 infection report persistent or recurring covid symptoms for several weeks or months. This notably includes younger and previously healthy individuals, as well as those whose original covid was mild or moderate (without hospitalization).

According to a British ONS survey published in April 2021, close to 14% of PCR-confirmed people (hospitalization rate 8%) reported symptoms lasting longer than three months (compared to 2% in the control group), of which about 60% reported “some limitation” and close to 20% reported “strong limitation” to their day-to-day activities.

According to another British study, published in Nature Medicine and based on somewhat different criteria, only 2% had symptoms lasting longer than three months.

A large Norwegian cohort study, covering 70,000 participants, found that one year after covid diagnosis, 16% still reported altered smell or taste, 14% poor memory, 13% fatigue, 10% shortness of breath, 7% reduced lung function, 8% brain fog, 5% heart palpitations, and 4% chest pain; all of these values are risk differences compared to a control group.

A French study suggested that long covid symptoms were associated only with the belief of having had covid, not with actually having had covid (i.e. it was a psychosomatic condition), but the study relied on mostly non-specific symptoms (e.g. back pain, sleep problems, digestive problems), and it relied on serology (antibodies), which may remain negative (or turn negative) in people who had mild covid, while it may be positive in people who had an asymptomatic infection.

B. Symptoms

Frequently reported symptoms include persistent coughing, moderate fever, general fatigue or exhaustion, shortness of breath, chest pain, hoarseness, heart palpitations, headaches, concentration problems, muscle pain, digestive problems, skin rashes and metabolic symptoms, as well as prolonged or chronic loss of taste or smell.

Some affected persons, including young people from around 30 years of age, report significant restrictions in their everyday life, such as exhaustion after climbing stairs or extended walks. Covid pneumonia might also cause, or exacerbate, asthma-like conditions.

One to two months after coronavirus infection, symptomatic Swiss army recruits (median age 21 years) still showed a reduction of up to 20% in their maximum lung performance. The cause of such a reduction in lung performance may be covid-induced pneumonia.

A case study of ten long covid patients, published in the journal Chest, found persistent exertional intolerance, including a significantly lower peak exercise aerobic capacity, impaired systemic oxygen extraction, and greater ventilatory inefficiency.

A European study found that, among hospitalized covid patients with olfactory dysfunction, about 5% had not yet fully recovered their sense of taste or smell after 6 months.

It appears likely that the omicron variant, which in most countries replaced the delta variant in December 2021, will pose a lower risk of long covid due to its much lower impact on the lungs and the olfactory sense.

C. Causes of post-acute symptoms

In general, symptoms of post-acute covid and long covid may be explained by the impact SARS-CoV-2 has on the olfactory support cells (e.g. loss of taste and smell), the throat (e.g. hoarseness, coughing), the lungs (e.g. shortness of breath, chest pain), the endothelium (e.g. reduced lung perfusion and gas exchange, POTS), and possibly on the immune system (e.g. auto-immune reactions), the neurological system (e.g. ‘brain fog’, ‘poor memory’), or the cardiac system (e.g. myocarditis).

In particular, there is increasing evidence that pulmonary endothelial dysfunction and possibly pulmonary micro-thrombosis may play a role in key symptoms of post-acute covid, including chest pain, shortness of breath, fatigue, exercise intolerance, dizziness and tachycardia (heart racing).

Studies have shown that Sars-CoV-2, which uses the ACE2 cell receptor present on endothelial cells, may cause endotheliitis (inflammation of blood vessels) and micro-thrombosis (micro blood clots), which in turn might give rise to pulmonary and cardiovascular post-covid symptoms (see this histopathological examination).

Severe cases of post-acute covid syndrome have been compared to POTS (Postural Orthostatic Tachycardia Syndrom). In April 2021, a US study for the first time could independently show that POTS is itself caused by or linked to endothelial dysfunction.

Other potential causes of post-acute and long covid symptoms might include neurological, metabolic and immunological conditions, including auto-immune reactions. However, additional studies will be required to clarify their potential role. A possible reactivation of latent herpes virus or Epstein-Barr virus infections has also been discussed as a possible explanation of some of the non-specific long covid symptoms (e.g. fatigue).

D. Diagnosis

While some symptoms of long covid are rather easy to diagnose (e.g. loss of taste or smell), other symptoms are more difficult to understand and also more difficult to distinguish from conditions not related to covid (e.g. fatigue or ‘brain fog’).

Pulmonary endothelial dysfunction may not be visible in standard x-ray and CT scans, nor in CT angiography scans and standard lung function tests, but may be visible in specialized gas-exchange tests and in lung ventilation/perfusion gamma scans (see annex below).

In some long covid patients, it was found that arterial oxygen saturation was normal (above 95%), but venous oxygen saturation was extremely low (about 25% instead of about 65%). This is a highly unusual clinical finding whose cause currently remains unknown. It could be related to endothelial dysfunction and might explain symptoms such as exhaustion and fatigue.

Sars-CoV-2 antibodies may or may not be measurable at the time of diagnosis, depending on the severity of the acute disease, the time since the acute disease, the age and sex of the patient, and the sensitivity of the antibody test assay (which ranges from 99% to 20%).

E. Treatment options

Note: Patients are asked to consult a doctor.

Several ongoing trials that focus on post-covid symptoms related to endothelial dysfunction or micro-thrombosis apply anti-coagulation therapy, using drugs such as apixaban or sulodexide. Other trials attempt to ‘calm down’ the immune system and a potential auto-immune response.

  1. UK HEAL-COVID trial on the treatment of long Covid (NHS, March 2021)
  2. Endothelial Dysfunction during the COVID-19 follow-up (ENDCOV, Jan. 2022)
  3. Endothelial dysfunction is the key of long COVID-19 symptoms (ACVD, Jan. 2022)
  4. A diagnosis for Long Covid (Jasmine Hayer, Medium, March 2021)
  5. Sulodexide in the early stages of COVID-19 (Ochoa et al., April 2021)

See also: The FLCCC I-RECOVER Protocol

F. Prevention and vaccination

To avoid the risk of post-acute covid completely, infection with the virus must be avoided. If a symptomatic infection does occur, early treatment options should be discussed with a physician to prevent progression of the disease. If covid symptoms nevertheless persist or return, post-covid tests and treatment options should be considered.

Since even mild covid can trigger long covid symptoms, and since vaccination cannot prevent infection and mild covid, vaccination in general cannot prevent long covid. According to a US study, vaccination reduced the risk of developing long covid symptoms by only 13%. An Israeli study suggested a significantly lower risk after vaccination, but the effect was only visible in people over 60, and was not significant in the adjusted analysis (see page 9 and table 3).

Furthermore, recent reports indicate that covid vaccines may themselves cause “long covid”-like conditions and Multi System Inflammatory Syndrome (MISC) in children, which is likely due to an immune response to the coronavirus spike protein.

The potential medical risk of long covid doesn’t justify political measures like lockdowns, as these measures aren’t effective in preventing covid and long covid.

G. Post-acute covid in children

According to an Australian study published in The Lancet, post-acute covid symptoms in children are rather rare (8%), generally mild (mild cough or fatigue), and mostly of short duration (3 to 8 weeks). About one third of children remained completely asymptomatic. A larger British study found that among 1,400 PCR-positive children, 1.8% experienced symptoms for more than 56 days.

A large Danish study of about 40,000 children (6-17 years) found that, compared to a control group, 0.8% of children with covid reported symptoms lasting longer than 4 weeks. However, a closer analysis of the study shows that in children who had had covid, prolonged loss of taste, loss of smell, respiratory problems, dizziness and fatigue were significantly more common than in the control group, affecting 10% to 30% of children older than 13 years (i.e. during and after puberty).

H. Comparison to post-viral syndrome

The so-called post-viral syndrome or post-viral fatigue is already known from other viral infections, including severe influenza. The occurrence of post-acute covid is therefore not entirely surprising or unusual, but it is nevertheless quite widespread and must be taken seriously.

J. The role of myocarditis

Initial studies reported inflammation of the heart muscle (myocarditis) in a very high proportion of mild and moderate covid cases. However, later studies could not confirm this finding, instead reporting generally mild myocarditis with a frequency comparable to influenza virus infections. Several covid autopsy studies have also found little evidence of myocarditis.

A study of about 1,600 US competitive collegiate athletes, published in JAMA Cardiology in May 2021, found a prevalence of symptomatic clinical myocarditis of 0.31% (i.e. 5 athletes); cardiac MRI increased the total prevalence of myocarditis to 2.3% (9 athletes had clinical myocarditis, 28 had subclinical myocarditis).

Several studies found that, in males younger than 40, the risk of myocarditis is higher after mRNA vaccination than after coronavirus infection (and vaccination doesn’t prevent infection).

In February 2021, cardiologist Donald Llyod-Jones, president-elect of the American Heart Association, stated that “there’s a lot less myocarditis than we originally thought there would be.” Nevertheless, in case of post-covid cardiac symptoms, patients should immediately consult a doctor.

See also: Setting the record straight: There is no ‘Covid heart’ (StatNews, May 2021)

K. Quality of research and media reporting

Many studies on post-acute covid are of poor quality. For instance, many studies include people without PCR or antibody confirmation; refer to non-representative patient cohorts; apply unsuitable diagnostic criteria; do not include a control group; or do not apply a symptom severity score. In addition, many media reports further exaggerate low-quality research on post-acute covid.

Thus, the public perception of long covid is likely to be distorted. Nevertheless, high-quality research and clinical experience show that true long covid is a real and significant health issue.


A. Perfusion and gas exchange in the lungs

Lung perfusion gamma scan in a young long covid patient one year after “mild” covid, showing significantly reduced perfusion in the upper right lung.

Reduced lung perfusion in a young woman one year after “mild” covid (Source)
B. Symptom duration

According to the British ONS, about 14% of PCR-confirmed covid patients continue to report symptoms after three months, of which 20% report a “strong limitation” to their daily activities.

Symptom duration in people with covid vs. control group (Source: ONS)
C. Symptom duration after “normal” pneumonia

After “normal” pneumonia, complete regeneration may also take one to three months. Therefore, a post-covid diagnosis may require specialized tests (see above).

Duration and severity (0-100) of symptoms after “normal” pneumonia (Metlay 1997)
D. Resources


  1. The Hidden Voices of Long Covid (Jasmine Hayer, June 2021)
  2. Researchers Investigate What COVID-19 Does to the Heart (JAMA, February 2021)
  3. The lasting misery of coronavirus long-haulers (Nature, September 2020)
  4. Long term respiratory complications of covid-19 (British Medical Journal, August 2020)
  5. Covid-19: Impact of long term symptoms will be profound (BMJ, August 2020)
  6. Three Months In, These Patients Are Still Ravaged By Covid’s Fallout (WSJ, July 2020)
  7. COVID-19 Can Last for Several Months (The Atlantic, June 2020)

See also

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