The typical symptoms, a contact with an infected person and a positive test are needed, in order to diagnose someone with Covid-19. According to Bulgarian doctors working at the frontline against Covid-19, things are different sometimes. In two or three cases, the Covid-19 tests were negative, although diagnostic imaging indicated Covid-19 infection and people had clinical picture of Covid-19. According to Bulgaria’s Chief State Health Inspector Dr. Angel Kunchev, the probability of a false-negative Covid-19 PCR test is between 3% and 5%. When the symptoms are in place and if we know the person who infected the patient, we can assume this diagnosis, even if the result of the test is negative, Angel Kunchev specified in an interview for BTV.