The physiological derangements in subjects suffering from long-term symptoms following a Covid-19 infection (Post-COVID-19 Syndrome) are poorly understood and evaluated. This study will recruit subjects with a clinical diagnosis of Post-Covid-19-syndrome) who are scheduled for either of lung function testing, cardiopulmonary exercise testing or cardiac ultrasound. Patients' symptoms will be correlated to physiological measures and compared to predicted values. In addition, in 20 patients, symptoms and physiological measures will be correlated to epigenetical alterations, or DNA-methylation patterns. In addition, a subset of patients will be examined a year after the baseline testing in order to follow the progress of the disease.

The physiological derangements in subjects suffering from long-term symptoms following a Covid-19 infection (Post-COVID-19 Syndrome) are poorly understood and evaluated. For example, the extent to which subjective symptoms correlate with physiological impairments are not known.

This study will recruit subjects with a clinical diagnosis of Post-Covid-19-syndrome) who are scheduled for either of lung function testing, cardiopulmonary exercise testing or cardiac ultrasound. Patients' symptoms will be correlated to physiological measures and compared to predicted values.

In addition, in 20 patients, symptoms and physiological measures will be correlated to epigenetical alterations, or DNA-methylation patterns. In addition, a subset of patients will be examined a year after the baseline testing in order to follow the progress of the disease.

Inclusion Criteria:

• Confirmed or clinically highly suspected Covid19-infection
• Symptom duration at least 12 weeks following first occurence of symptoms
• No other disease that better could explain the symptoms than Covid19

Exclusion Criteria:

• Age <18 years
• Unability to perform a maximal exercise test
• Unability to understand written or spoken Swedish

All subjects fulfilling inclusion criteria and no exclusion criterion referred for a clinical examination at the specified clinic will be informed about the study and inquired regarding participation.

As part of a national collaboration on Post Covid19, coded (deidentified) data may be shared with other selected researchers in accordance with the ethical permission obtained by the Ethical Review Board.