Government influenza pandemic preparedness strategies warned that school closures would place a significant pressure on health workers, handicapping their ability to come into work at a time when they are most needed.

Teaching unions also expressed concerns over the prospect of an increase in class sizes, warning it could even make the risk of infection worse.

Kevin Courtney, Joint General Secretary of the National Education Union, said: "A cramped classroom will not keep pupils safe, potentially doing more harm than good, and arguably work directly against the 'social distancing' recommended in the action plan. It will not provide peace of mind for parents."

Care homes have been advised to go into lockdown in the event of a major coronavirus outbreak, with visitors banned and sick patients confined to their bedrooms.

Providers across the country have been issued with new guidance to prevent the virus from spreading among vulnerable and elderly residents, and health chiefs urged relatives not to "go and visit your auntie in a care home" if suffering from a cold or flu-like symptoms.

At least two care homes in Britain have temporarily shut over concerns that residents may have come into contact with a confirmed coronavirus case. Death rates have shown that Covid-19 poses a far greater danger to the elderly and those suffering underlying health problems. Care homes are also feared to be at heightened risk because of the close living conditions.

Professor Chris Whitty, the Government's chief medical officer, has said officials are keen not to take stringent measures, such as banning visitors from care homes at which no cases have been identified, too early because of the social cost involved.

However, guidance issued by the Care Provider Alliance, the industry body representing adult social care providers in England, describes how care homes should go into effective lockdown if a resident is diagnosed with coronavirus.

The Coronavirus Infection and Prevention Toolkit document says patients should be kept in their bedrooms rather than automatically being sent to hospital. "If it is not possible to isolate people – for example, those who need dementia support or other specialist needs – symptomatic individuals should be cared for in an area that can be separated from those who are unaffected," it adds.

The guidance also advises care providers to consider restricting visits from all relatives until the outbreak is over and refuse to admit any new clients. "It may be necessary to contact regular visitors and ask them not to visit the care setting during the outbreak of infection," it says.

Care providers are also told to restrict the use of new agency staff in the event of a coronavirus case to lessen exposure to the disease.

"If this is unavoidable, block-book staff during the outbreak to limit the numbers of individual agency staff potentially affected," the advice adds. "If staff are taken ill as a result of being exposed to the infection, you should follow national and local guidance on how to prevent the spread of the infection."

Wales' chief medical officer, Dr Frank Atherton said: "If you think about the most vulnerable populations, they are often in nursing homes or care homes. I think we need to intensify the advice to people that, if you have a cold or flu-like illness, don't go and visit your auntie in a care home."

In the US, an outbreak of coronavirus in a nursing home near Seattle has left one resident dead and four others in hospital, three of them in critical condition. Of the home's 108 residents and 180 staff members, more than 50 have shown signs of possible Covid-19 infections, officials said.

The Government's chief scientific and medical advisers have told holidaymakers to go abroad wherever they want – as long as they make sure their destination has decent healthcare.

The advice follows the cancellation of hundreds of flights by airlines, with tourists and business travellers either scrapping travel plans or refusing to commit to bookings. Coronavirus has hit the airline industry particularly hard, with the value of the world's biggest airlines plunging by billions of pounds.

Consumer groups warned that families who have booked to go on Easter holidays have been left confused in the wake of the outbreak, unsure over whether their trips are covered by insurance, whether it is safe to travel and whether flights will be cancelled anyway.

One airline expert warned that the cost of some flights could rise, with routes scrapped to match dwindling demand.

The chief advisers on the virus moved to clear up confusion over international travel at a news conference unveiling the Government's coronavirus action plan.