Coronavirus: the picture across West Yorkshire
Boris Johnson says hospitals are likely to face pressure "for weeks" amid staff shortages
Boris Johnson has warned coronavirus is likely to leave the NHS under "considerable" pressure for weeks to come, as staff shortages threaten standards of care.
It's as face masks are reintroduced in classrooms, with increased testing in schools, to try to slow the spread of the Omicron variant.
Train companies have also been forced to cancel services as commuters began returning to work, because of staff shortages.
We've been taking a look at the situation in West Yorkshire.
Hospitals asking people to think twice about A&E
Hospitals across Bradford and Airedale have asked people to avoid using A&E if possible because services are facing high demand.
The chief nurse at Bradford Teaching Hospitals, Karen Dawber, has asked patients to consider ringing 111, self care or visiting pharmacists to keep numbers down.
It's after the Prime Minister pleged to "make sure that wee look after our NHS any way that we can" with hospitals across the country declaring critical incidents.
Boris Johnson warned "there's no question Omicron continues to surge through the country" and he added: "I think we've got to recognise that the pressure on our NHS, on our hospitals, is going to be considerable in the course of the next couple of weeks, and maybe more."
Face masks for pupils in classrooms again
Pupils returning to schools in West Yorkshire after the Christmas break will have to wear face masks for the next few weeks.
There's also going to be increased testing on sites, as part of efforts to slow the spread of Omicron among younger people.
But headteachers have warned that staff shortages in the new term caused by teachers isolating because of positive lateral flow tests will be "challenging" for some schools and could lead to more pupils learning online.
Geoff Barton, general secretary of the Association of School and College Leaders, said that school bosses had responded to the reintroduction of face coverings for an initial two-week period with a "kind of weary, pragmatic acceptance that if that's what we need to do to try to reduce transmission then that's what we shall do".
He added: "I think most people will hope that that's a price worth paying to keep more young people in school, but ultimately that will come down to whether we've got enough staff when term starts tomorrow."
Meanwhile, one school in Otley has delayed the start of term by a day, to allow pupils to take a coronavirus test at home.
Prince Henry's Grammar School opened a testing site for pupils on Tuesday, ahead of lessons restarting on Wednesday.
Trains cancelled amid staff shortages
Rail passengers were hit by disruption on the first working day of the year in England and Wales due to a combination of faults and coronavirus-related staff shortages.
Northern was running an amended timetable due to "the impact of COVID" and the availability of train crew.
No London Overground services were able to run between Clapham Junction and Surrey Quays on Tuesday morning due to a fault on a train.
National Rail Enquiries warned passengers that a "problem under investigation" between Darlington and York was causing disruption between the stations.
This affected CrossCountry, London North Eastern Railway and TransPennine Express services.