The number of secondary school-aged children catching coronavirus is the highest since schools reopened after the summer holidays.
Public health data shows infection rates across Hertfordshire are the highest they have been since lockdown restrictions were eased with the virus spreading in schools.
But there are signs in some parts of the county that the virus is spreading to larger numbers of adults; particularly those aged in their 40s.
Downing Street said it is keeping a "very close eye" on increasing case rates across England and Professor Neil Ferguson has warned it is "critical" the Covid-19 booster programme is accelerated.
In Hertfordshire, 12,537 people have tested positive for Covid in October, with the infection rates highest in those aged between 10 and 19.
The area of the county with the highest rate currently is St Albans district - although this was one of two districts in Hertfordshire that has actually recorded a drop in cases over the last week; albeit a tiny drop.
In Hertsmere, the rate sits at 479.8 cases per 100,000 poulation over the seven days to October 15. This is the equivalent to 506 cases.
A Government Covid dashboard map shows rates are being driven by higher levels of cases in Borehamwood, Radlett, and parts of Potters Bar.
Our tables show exactly how many cases have been recorded in your neighbourhood between October 8 and 14.
The majority of recent cases in Hertsmere involve 10-14-year-olds (a rate of around 1,700), Public Health England data shows, followed by 15-19-year-olds.
The next highest rates are in those aged between 35 and 50 (between 400 and 550).
Overall in Hertfordshire, infection rates are broadly in line with the rest of the country, outside of London.
The highest rate in England is in Bath and North East Somerset where the infection rate is 877.5, followed by Somerset West and Taunton at 872.5, and Ipswich at 861.2.
The lowest rate in England is currently in Southwark at 143.7.
In Hertsmere, just under 30 per cent of the over 12 population are unvaccinated against Covid.
In age groups above 45, uptake is over 80 per cent.
As of October 18, 28.7 per cent of Hertsmere's 12 to 15-year-olds had received one Covid vaccination.
An uptake of 29.1 per cent across Hertfordshire is the third highest across all of Englad's upper-tier local authorities.
According to the latest Government dashboard data, West Hertfordshire Hospitals NHS Trust was caring for 28 Covid patients as of October 12, including five on ventilation.
The trust has recorded five Covid deaths in October, including on October 15, 16, 17, according to NHS England data.
These were patients who have died at a hospital within the trust and either tested positive for Covid-19, or where no positive test result was received for Covid-19, but Covid-19 was mentioned on their death certificate.
The trust has recorded 950 Covid deaths since the pandemic began.
On Tuesday, the Government said a further 223 people had died across all settings within 28 days of testing positive for Covid-19, bringing the UK total to 138,852.
While the numbers are often higher on Tuesdays because of a lag in reporting deaths and cases over the weekend, this is the highest figure for daily reported deaths since March 9.
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