Coronavirus infections declined by more than a fifth in the second week of January, but the public health agency RIVM warned that new mutant strains were on the increase.

The total number of infections was 21.5% lower at 38,776, while the positive test rate also fell from 12.9% to 11.7%. The reproductive number R increased slightly to 0.98, indicating that the spread of the virus is barely declining.

The B-117 variant of the virus, first detected in the UK in September, is thought to be responsible for around 10% of infections at the moment, but around 30% more infectious than the most common strains.

Virologists have warned that it could become the dominant strain by March, leading to a fresh wave of infections and hospital admissions if no preventive measures are taken.

The downward trend was also reflected in the latest daily figures, which recorded 4,335 new infections in the last 24 hours, 11% fewer than a week ago and well below the seven-day average of around 5,500. However, the number of Covid-19 patients in hospital increased for the third day in a row to 2,445, an increase of 16.

Under 30s down

Infections declined in all age groups last week, but particularly among people under the age of 30. For 15 to 19-year-olds cases were down by 36% to 268 per 100,000 people, compared to a figure of 677 in the week before Christmas.

The 25 health board regions varied from an infection rate of 145.5 infections per 100,000 in Haaglanden, which covers The Hague, to 284.8 in Twente. Nine of the 25 areas had an infection rate below 200 per 100,000 compared to just one a week ago.

A total of 1,348 people were admitted to hospital, a decrease of 17.2% from the previous week, while intensive care admissions were down by 15.7% to 252. Another 608 deaths were recorded compared to 743 the previous week, a fall of 18.2%.