Inclusion Criteria:  Age 18 to 65 years SARS-CoV-2 infection proven by a PCR test at least 12 weeks prior to inclusion Only cases: Referred to the Clinic of long-covid located in Region Zealand, Denmark  Exclusion Criteria:  Need of being on a respirator during infection with SARS-CoV-2 Only controls: complain about long covid 12 weeks or more after proven infection with SARS-CoV-2