The message from experts is: if you feel unwell, stay at home.

The guidance was issued as Britons prepare for their least restricted Christmas since COVID curbs and subsequent guidance forced some families to stay apart.

The NHS has come under intense pressure in recent weeks, with the number of people in hospital rising by two-thirds in a week, NHS England data showed.

The UK Health Security Agency (UKHSA) has urged anyone with symptoms to stay at home if they feel unwell and advised them to wear a mask in enclosed spaces, such as on public transport or supermarkets.

Dr Jamie Lopez Bernal, consultant epidemiologist for immunisation and countermeasures at UKHSA, said: "If you are unwell this winter, please try to stay at home and avoid contact with other people, particularly elderly or vulnerable people - this will help stop infection from spreading."

A "near record" demand for NHS 111 services, thought to be partly driven by parents' concern about Strep A, has contributed to the pressures heaped on healthcare workers.

The data revealed that an average of 1,939 people with flu were in hospital each day last week, up 67% on the 1,162 the previous week.

By comparison, the daily average at the end of November was 482.

Hospital chiefs said the difficulties dealing with the resurgence of viruses had been "aggravated" by strikes by nurses and paramedics, with healthcare workers announcing another two days of walkouts in January yesterday.

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In the week before ambulance workers went on strike, ambulance handover delays hit a new high, as one in four patients were waiting more than an hour to be handed to A&E teams.

NHS trusts have a target of 100% of patients being handed over within 60 minutes, and 95% in the first 30 minutes.

Calls to NHS 111 last week were up almost 60% from the equivalent week in 2021, and increased to 721,301 last week from 706,129 the week before.

The rise in demand is understood to be partly due to parents worried about symptoms of Strep A.

Cases of scarlet fever, an infection linked to Strep A, are more than twice as high as previously thought, the UKHSA said on Tuesday.