The number of people testing positive for coronavirus increased by more than 35% in the second week of December, according to the latest update from public health agency RIVM.

The rise was underpinned by a 37% increase in testing, with nearly 440,000 tests being carried out compared to 321,000 in the previous week.

However, the positive test rate went up to 12.0% while the R number, which measures the reproductive rate of the virus, was reckoned to have climbed to 1.24 at the end of November. Any value above 1 indicates that the number of infected people is increasing.

The RIVM also said on Monday that computer problems meant around 6,000 cases were missing from the daily figures for the last three days. If those cases were included the week-on-week rise would be around 50%. On Tuesday another 6,682 cases were reported, 1,800 fewer than on Monday and 3,200 below Sunday’s figure.

Currently 1,954 Covid-19 patients are in hospital, 72 more than on Monday, while the number in intensive care has gone up by 21 to 524.

The spike in the value of the R number is believed to be one of the main reasons for the government’s decision to impose a full five-week lockdown from Tuesday morning.

Urgent call

NOS reported that prime minister Mark Rutte convened an emergency council of ministers on Sunday following a telephone call on Friday evening from Jaap van Dissel, the RIVM’s head of infections disease control, who warned him that the upward spiral in cases would continue unless stronger measures were taken.

Other numbers in the RIVM’s weekly reported also indicated that cases were on the increase. In the second week of December 1,480 patients were admitted to hospital with Covid-19 and another 222 to intensive care. Both numbers were up by more than 20%.

Around the 25 health board regions the greatest concentration of cases was in Limburg-Noord, with 440 infections per 100,000 people in the last week. Utrecht and Gelderland Midden also had more than 400 infections, while Friesland had the lowest proportion at 167.4.

The figures also showed infections spreading strongly among school-age children. Among 10 to 14-year-olds the rate increased by 44% to 452 per 100,000, while five to nine-year-olds recorded a 62% rise. Schools and nurseries are now identified as the source of infection in more than 10% of cases where the origin is known.