The risk is very high that virus mutations will continue to spread in the EU - which could result in an increased number of hospital admissions and more deaths.
This is stated by the EU's infection control authority ECDC in a new report.
At the same time, Sweden has increased its monitoring of which virus variants are in circulation.
There are now confirmed cases of mutated virus in all regions of the country except Gotland.
By far the most common mutation is the so-called British virus variant.
According to the Swedish Public Health Agency, there were 423 confirmed cases last week.
However, since only a limited proportion of the positive covid tests are further analyzed, it "does not give a true picture of the current prevalence in the country", according to the authority.
The infection control doctor: We are worried
When random checks were carried out in four regions, during the first week of February, a suspected British mutation was found in 9-20 per cent of covid cases in the different regions.
In Gävleborg, 19 percent of all those who tested positive for covid-19 last week were infected with the British virus mutation.
- On Thursday, the number was 99 infected in the region and late on Friday night we received figures that there were a total of 160 infected, says infection control doctor Shah Jalal to SVT Gävleborg.
In addition, the number of hospital admissions has increased in the region.
- The British virus variant is more contagious than the usual and therefore we are worried, says Shah Jalal.
Concerns about sports holidays
In the coming sports holiday season, there is concern in some quarters that the more contagious virus variants will become more widespread.
In the Sälen area in Dalarna, several cases of the British mutation have been discovered and extra sampling awaits during the high season.
- We are testing more for this virus variant and those who work in Sälen are on their toes, says Helena Ernlund, assistant infection control doctor in the region, to SVT Dalarna.