NHS figures revealed a jump in coronavirus patients in Northamptonshire hospitals ahead of Chief Medical Officers' raising the UK's Covid-19 Alert Level.
Latest data showed more than 100 Covid-positive patients in Northampton and Kettering hospitals following ten admissions in a single day at KGH.
None are so far infected with the Omicron variant although local officials echoed scientists' warnings about the strain's potential to put more pressure on hospitals.
The UK's four Chief Medical Officers recommended moving from Level Three to Level Four — the second highest level — on Sunday December 5, warning: "Transmission of Covid-19 is already high in the community but early evidence shows that Omicron is spreading much faster and that vaccine protection against symptomatic disease from Omicron is reduced.
"Data on severity will become clearer over the coming weeks but hospitalisations from Omicron are already occurring and these are likely to increase rapidly.
"The NHS is currently under pressure mainly driven by non-Covid pressures. With a variant spreading with increased transmissibility and reduced vaccine effectiveness, we are likely to see this pressure rise soon."
The Alert Level has now been raised to Level Four and the Prime Minister addressed the nation last night (December 12) to say all over-18s would be offered a booster jab by the end of the year to tackle the tidal wave of Omicron.
Up to 117 Omicron cases had been found in West Northamptonshire by Friday, although numbers are rising rapidly across the country.
Public Health Northamptonshire director Lucy Wightman added: “It is now clear that the variant has spread within the community, mainly through a series of events and within households.
"Currently. known Omicron cases have only been detected in a reasonably young age range and to date no one locally has been hospitalised.
"However we are still learning about Omicron and the related risks. So the sensible option is to keep calm, exercise caution, and follow the new government Plan B rules."
The Plan B rules:
■ Since Friday, face masks are required in more public settings — including theatres and cinemas — as well as shops and public transport
■ From today (December 13), people are being asked to work from home where possible
■ From Wednesday, the NHS Covid Pass will be required in nightclubs, indoor unseated venues with more than 500 people, unseated outdoor venues with more than 4,000 people and any event with more than 10,000 people
The number of patients being treated for Covid-19 in Northamptonshire's two main hospitals reached 104 by Tuesday (December 7), rising from 89 a week earlier.
NHS England data showed the number of Covid patients in Kettering General Hospital nearly doubled from 28 to 52 over six days with ten admitted in one 24-hour period from 8am on Monday — that last day for which data is currently available.
Half the 24 patients in critical care beds in the two hospitals were being treated for the virus.
Seven people are so far confirmed to have sadly died while being treated for the virus at KGH during the first eight days of December, plus another six at NGH.
Daily figures published by the government say 4,400 people have tested positive in Northamptonshire during the last seven days. That compares to a weekly figure of 3,200 a month ago.
Health chiefs are underlining messages around regular testing and vaccinations to help slow the virus' spread.
Mrs Wightman added: “I know this will be hard for many people, but by following the additional rules and reducing your contacts in the workplace you will help slow transmission.
"Vaccines are proven to offer high levels of protection, and there are good reasons to believe that a full course of vaccine treatment will protect against severe disease and death with Omicron as well."
■ Lateral flow tests can be ordered online HERE or collected from local pharmacies.
“Testing is a really important tool in our armoury and it’s vital to take lateral flow tests at least twice a week.
"Around one in three people with Covid-19 do not have symptoms and these rapid lateral flow tests help find cases in people who have no symptoms but are still infectious and can give the virus to others.
“It’s also important to stay at home if you're not feeling well. If you have any Covid-19 symptoms, however mild, do book a PCR test."