Mass testing of people in a small town near Rotterdam where the more infectious variant of coronavirus had formed a cluster at a primary school has revealed that the new strain is not extremely widespread.

In total, 45,000 out of 60,000 residents in Lansingerland have so far forward to be tested after the outbreak of the B-117 variant of the virus.

Researchers from the local health board and Erasmus teaching hospital have analysed half the tests so far, and found 242 people with coronavirus.

Some 12% of them had the B-117 or ‘British’ variant, but that percentage was far lower among people with no connection to the Willibrordusschool. Only one case was found in the adjoining school buildings, the researchers said.

Officials say that the new variant is responsible for some 10% of infections nationwide.

The outbreak at the school involved 46 adults and children and would now appear to be under control, officials said. The source of the infectious has not yet been identified.

‘This emphasises the importance of keeping to the rules,’ health board doctor Ewout Fanoy told broadcaster NOS. ‘Even if you don’t have symptoms, you can be infected with coronavirus and thus infect others.’