The UK government has outlined new measures to control the spread of the COVID-19 coronavirus as the number of cases reported reaches 40.
It said a fifth of the workforce could be off sick and the government has urged people to work from home if possible.
The Ministry of Defence would provide support to the civilian authorities if requested.
Asked about the possibility of staff shortages in the police force, Prime Minister Boris Johnson said: "The army is of course always ready to backfill as and when, but that is under a reasonable worst case scenario."
Mr Johnson’s government has said it was considering closing some schools, cancelling sporting events and curbing travel on public transport.
Mr Johnson told reporters it would be “business as usual” for “the vast majority of people”.
He said: "I fully understand public concern about the global spread of the virus and it is highly likely we will see a growing number of UK cases. Keeping the UK safe is the government’s overriding priority. We will make sure the NHS gets all the support it needs. Our country remains extremely well prepared as it has been since the outbreak began several months ago.”
The coronavirus, which emerged in the Chinese city of Wuhan in December, has spread around the world with 90,000 cases globally and infections in 77 countries, the latest of which has been Ukraine.
The vast majority of the deaths - 2,943 - have been in China but there have been 75 deaths outside of Chinese borders and a worrying spike in cases in Iran and Italy.
Mr Johnson chaired a Cabinet meeting on Tuesday, 3 March, before announcing a coronavirus battle plan.
At the forefront of the plan was a strategy of “social distancing” which would involve people working from home, not travelling unnecessarily or socialising in large numbers.
The National Police Chiefs' Council lead for civil contingencies, Deputy Chief Constable Paul Netherton, said: "If required, we have tried and tested plans that ensure continuity of policing during times of capacity issues or increased demand. These plans can include moving officers around the country, changing shift patterns and the use of the Special Constabulary."
The new Chancellor, Rishi Sunak, has been told to redraft his Budget - due to be announced on 11 March - in order to focus on combating the coronavirus and alleviating the burden on businesses which are due to suffer as a result of the reduced footfall.
Retailers, publicans, cinema owners and transport companies are all expecting to face a major hit if people heed warnings and stay at home.
But the social media reaction suggests that many people in Britain believe the coronavirus has triggered an over-reaction.
Many Twitter users have pointed out that more people have died from influenza than COVID-19 and have highlighted the fact that the illness is only believed to be fatal for the elderly or those with underlying health problems.
On Monday Mr Johnson said it was likely there would be a “very significant expansion” of the virus across Europe in the next few days.
Health Secretary Matt Hancock told the BBC on Tuesday: “Right now, we do not recommend the cancelling of mass events and schools as well should not be closing unless there is a positive case and the schools have the advice to close. There maybe things we have to do down the line that we don't want to, but we will need the powers to do that hence proposing emergency legislation.”
Among events which could be under threat are next week’s English Premier League fixtures.
The media-driven hysteria has also led to a number of racist incidents against people from East Asia.
The Metropolitan Police are investigating a racially motivated assault on a Singaporean student, Jonathan Mok, 23, in London.
Mr Mok recounted on Facebook how he was punched in the face by a youth who said: "I don’t want your coronavirus in my country."