Up to a fifth of the workforce may be off sick during the peak of a coronavirus epidemic in the UK, the government says in its latest plans.

Police may need to focus on only the most serious crimes and maintaining public order if the virus spreads.

The military could also provide support to emergency services if needed.

The government’s response is in its first stage – containing the outbreak – with the number of UK cases rising from 39 to 51 on Tuesday.

It is “highly likely” the UK will see further infection than at present, Prime Minister Boris Johnson has warned, and the next phase of government contingency plans will be to do with delaying the spread of the virus.

If the coronavirus, which causes Covid-19, becomes widespread, some non-urgent hospital care may be delayed to focus on treating those who are infected, while recently retired doctors and nurses may be called back to work.

Other possible measures include school closures, reducing large-scale gatherings and working from home.

Prime Minister Boris Johnson said the government was committed to doing “everything possible” to “prepare for all eventualities” and its priority was keeping the country safe.

Speaking in the House of Commons later, Health Secretary Matt Hancock said it was “becoming more likely we will see widespread transmission” of the virus across the UK.

He said that tackling the spread was “a national effort”, adding: “We need everyone to listen to and act on official medical advice.”

About 90,000 people have been infected globally since the outbreak of Covid-19, with cases in more than 50 countries and more than 3,000 deaths.