Guidance on criteria for assessment of freedom from infection in covid-19
The Swedish Public Health Agency has developed national criteria for assessing freedom from infection in covid-19.
The PCR technology used in tests to detect viruses cannot distinguish between viruses capable of infecting cells and viruses that have been neutralized by the immune system and therefore these tests cannot be used to determine whether someone is contagious or not. RNA from viruses can often be detected for weeks (sometimes months) after the illness but does not mean that you are still contagious. There are also several scientific studies that suggest that the infectivity of covid-19 is greatest at the beginning of the disease period.
The recommended criteria for assessing freedom from infection are therefore based on stable clinical improvement with freedom from fever for at least two days and that at least seven days have passed since the onset of symptoms. For those who have had more pronounced symptoms, at least 14 days after the illness and for the very sickest, individual assessment by the treating doctor.
The criteria have been developed in collaboration with representatives of the specialty associations in infectious disease medicine, clinical microbiology, hygiene and infection control. These have most recently been discussed in the group at a meeting on 19 April 2021 due to the new virus variants. The assessment was then that no update was needed. The recommendations will be updated as new knowledge about covid-19 infectivity is added.