The number of flu patients in England jumped by more than a third over Christmas, with more than 1,000 people in hospital with the virus in the run-up to the current strike action by junior doctors.

Covid patient numbers are also continuing to rise, though norovirus levels appear to have peaked.

The figures give a snapshot of pressures on hospitals in the week to December 31, a time when the NHS was finalising its contingency plans for dealing with the six-day strike by junior doctors which began on January 3.

An average of 1,312 people were in hospital each day last week with flu, including 81 in critical care beds, according to NHS England.

The total is up over a third (39%) from 942 in the previous week and more than double the 648 recorded a fortnight earlier.

It is the highest figure so far this winter but still well below the equivalent number at this point a year ago – 5,441 – when the UK was in the middle of its worst flu season for a decade.

The number of hospital patients testing positive for Covid has increased for a fifth week running, with an average of 3,929 each day in the week to New Year’s Eve, up 8% from the previous week and more than two-thirds (68%) higher than at the start of December.

Norovirus levels, though slightly higher than at this point last year, have fallen in the latest figures, with an average of 377 adult hospital beds filled last week by patients with diarrhoea and vomiting or norovirus-like symptoms.

This is down 16% from 451 beds the previous week and a third lower (33%) than a fortnight ago.

The latest industrial action by junior doctors began at 7am on January 3 and runs until 7am on January 9, making it the longest of its kind in NHS history.

It follows a 72-hour walkout in the week before Christmas.

Both strikes are part of a long-running dispute over pay, which has already seen 1.2 million inpatient and outpatient appointments rescheduled.

Professor Julian Redhead, NHS England’s national clinical director for urgent and emergency care, said the health service has started 2024 “in a very difficult position”, while praising the “incredible hard work” of staff for dealing with rising levels of winter viruses on top of industrial action plus a spike in demand following the Christmas bank holidays.

He said: “We know the pressure is not going to let up any time soon, with four more days left of the longest ever consecutive strike action taken in the history of the NHS, and flu season not expected to peak in the near future.

“Although we have extensive preparations in place for strikes, and emergency care will continue to be prioritised, there is no denying the NHS has started the year in a very difficult position.

“This latest round of strike action will not only have an impact on this week but will have an ongoing effect on the weeks and months ahead, as we struggle to recover services and cope with heavy demand, but as ever I would urge the public to get their flu and Covid vaccines if they are eligible, and continue to use 999 or A&E in an emergency, and 111 online for any other conditions.”

The new figures on the performance of hospitals in England also show that 29% of patients arriving by ambulance last week had to wait more than half an hour to be handed over to A&E teams.

This is up from 23% the previous week, but is not the highest so far this winter, which was 34% in the week ending December 10, and is some way below the figure at this point last year (44%).

A total of 24,384 hours were lost last week to ambulance handover delays that took longer than 30 minutes to complete, compared with 54,853 hours in the equivalent week last winter.

Meanwhile, an average of 11,478 hospital beds per day were occupied last week by people ready to be discharged, up slightly from 11,439 the previous week but lower than 12,940 at this point a year ago.

Some 41% of people ready to leave hospital last week were actually discharged each day, down from 50% a week earlier when staff made extra effort to get medically fit patients home for Christmas.