The coronavirus infection rate in Hertfordshire fell last week and is well below the national average, suggesting it should avoid being placed in the highest tier of restrictions.

Prime Minister Boris Johnson has announced that when lockdown ends next week, England will return to a regional, tiered system, with each one more strict than the next.

But how will officials decide which tier Hertfordshire goes into?

The government has published a list of key factors to be considered. Here’s how Hertfordshire is faring.

Age

The first question is how Covid-19 is affecting different age groups – especially over-60s, who are most likely to suffer severe illness, resulting in hospitalisation or death.

In Hertfordshire, the latest data which includes ages is for the week up to November 11. That week, 16.8 per cent of confirmed cases were in residents aged 60 or above.

This was more than twice the England average of 8.2pc.

Since late September, the county’s proportion of confirmed cases in over-60s has fluctuated, but overall there has been a slight upward trend – and there are signs the virus is beginning to spread through older groups in Herts at a faster rate.

In the seven days to November 11, the age groups with the highest infection rates were 20-29 and 30-39, as has consistently been the case since late September.

However, in late September and early October, the next worst-affected group was teenagers, whereas in recent weeks the spread in residents in their 40s and 50s has overtaken the spread among teenagers.

Case rate

The second consideration is the rate at which cases are rising or falling.

On September 30, Herts had 414 confirmed cases, giving an infection rate of 34.8 cases per 100,000 people.

Four weeks later it had more than tripled, to 1,341 cases and an infection rate of 112.7.

Another four weeks later, on November 18 – the most recent verified data – cases had risen to 1,833, giving an infection rate of 154.1. However, it fell slightly on the previous week and is well below the national average of 228 infections per 100,000.

In St Albans, which had 211 cases as of November 18, the infection rate was slightly below the countywide figure. The figure in the city was 142.1 cases per 100,000 people.

Stevenage, with 125 cases, had an infection rate of 142.3.

Welwyn Hatfield had 139.8 cases per 100,000 people. North Herts was even lower, at 122.

Watford, however, had an infection rate of 186.4 cases per 100,000 people. Hertsmere’s figure was 163.

Positive results

The third factor is the proportion of tests being carried out which come out positive.

In Herts, the percentage of positive tests has risen every week since September, even when fewer tests were done.

In the week to September 30, 1.8pc of cases came out positive. By the week ending November 11, it had risen to 6.5pc.

Hospital beds

The final issue is NHS occupancy.

At the East and North Herts NHS Trust, the number of hospital beds occupied by Covid-19 patients has risen every week since early October.

On October 6, there were just two Covid patients. By November 17, there were 25.

At the West Herts Hospitals NHS Trust, the number has also risen. On October 6, there were 23 coronavirus patients. By November 17, there were 68.