The man in his 30s was found on Wednesday to be infected by the new coronavirus. Two people who had had contact with the man tested positive the following day.

Therefore, the man's contacts are now mapped during the flight from Milan to Stockholm and the train journey on to Gothenburg. The infection guard tries to contact all people who have sat two rows in front, behind or beside the man.

But how does the infection tracking really go into detail? Signar Mäkitalo is an infection prevention physician in the Gävleborg Region.

- You start by asking what day the patient got sick and find out what the person did then. Then you go through day by day and identify people who have been close to the patient and make contact with them.

"Following the onion principle"

According to Signar Mäkitalo, people are searching for people who have been within two meters of the infected person during the period when the person has had disease symptoms.

- There are studies from aircraft where we have looked at people with tuberculosis, who seem to be infected in similar ways. There we have seen that there are two rows in the front and two rows in the rear that are interesting. If you do not find anything on those people, it is extremely unlikely that other people would have received it, he says and continues:

- Sometimes you can expand for various reasons, sometimes not. You follow the onion principle.

Examines the nearest circuit

By the principle of closure, Signar Mäkitalo means that they begin by investigating the closest circle around the infected, those who have spent most time with the person.

- If you find someone who is infected there you can go to the ring outside, the ones that the patient has met a little less. But if you do not find anyone in the next ring you can cancel.

If the infection protection assesses that there is a risk that a person is infected, they have close contact with the person for 14 days.

- They agree whether they can work or not and if they get symptoms they should contact us immediately, says Signar Mäkitalo.