The different diagnosis groups and their reasons for inclusion in the study.
| ICD- code | Diagnosis | Reason for inclusion |
| J06.9 | Acute upper respiratory tract infection, unspecified (URTI) | Similar symptoms with COVID-19 |
| J10 | Influenza, seasonal influenza virus identified | Similar symptoms with COVID-19 |
| N30 | Acute urinary tract infection (UTI) | Reference diagnosis |
URTI and influenza were chosen because of their similarity with COVID-19 symptoms, where many patients sharing the symptoms were likely to seek medical care. UTI was chosen as a reference group, as the number of patients was estimated to be unaffected by the COVID-19 pandemic.
ICD, International Classification of Diseases.