LONDON (AP) — British authorities laid out plans Tuesday to confront a COVID-19 epidemic, saying that the new coronavirus could spread within weeks from a few dozen confirmed cases to millions of infections, with thousands of people in the U.K. at risk of death.

Officials hope the most drastic measures won't be needed. Britain may not be able to stop the virus, but it has one vital advantage in fighting it: a head start.

Unlike harder-hit neighbors such as Italy or France, the U.K. has seen just 51 confirmed cases of the new illness and little social disruption. Health officials have advised people to work, socialize and travel as usual — as long as they remember to wash their hands often in warm soapy water.

Prime Minister Boris Johnson said it was "highly likely" the number of coronavirus cases in Britain will grow.

"Our plan means we're committed to doing everything possible, based on the advice of our world-leading scientific experts, to prepare for all eventualities," he said during a news conference at 10 Downing St.

U.K. officials say if they can't contain the virus, they believe they can at least slow its spread.

"There are a number of measures that could be taken to try and reduce the peak, and flatten it a bit, so that we haven't got such sharp number of people (sick) at any one time." said Patrick Vallance, the government's chief scientific adviser.

Johnson's government on Tuesday unveiled a 25-page "action plan" for a worst-case scenario in which retired doctors and nurses could be called back to work, police might stop investigating minor crimes and local authorities could struggle to deal with the burden of extra deaths.

It said one-fifth of the U.K. workforce could be off sick, putting business, schools and hospitals under heavy pressure.

Johnson's government has been accused of being slow to respond to the outbreak, which was first identified late last year in China. The outbreak has infected more than 90,000 people around the world, the vast majority still in China, killing some 3,100 people.

British experts have previously said a worst-case scenario could see 80% of the U.K's 66 million people become infected with the coronavirus, though they believe the infection rate is likely to be lower.

England's chief medical officer, Chris Whitty, said Tuesday about 1% of people who get the virus might die but it varies by age group, with those over age 80 at greatest risk.

So far, Britain is not recommending any of the measures seen in some harder-hit nations, such as cancelling sporting events and other mass gatherings, closing large numbers of schools and universities and barring visitors from some countries. It isn't even advising people to stop shaking hands.

But U.K. authorities said more disruptive public health measures could put into effect if the situation worsens.

Authorities said they may have to close schools, cancel large public events and tell significant numbers of people to work from home as part of "social distancing strategies" designed to delay the spread of the virus until summer, when flu season is over and pressure on the health service lessens. Class sizes at schools might have to be increased if teachers fall ill.

If the virus spreads widely, the government would consider more drastic measures such as rationing medicines and focusing police resources on "responding to serious crimes and maintaining public order."

The document raises the prospect that the U.K. could have many more deaths than in a typical year and says the government "will provide advice to local authorities on dealing with this challenge."

Devi Sridhar, professor of Global Public Health at the University of Edinburgh, said the U.K. had time to learn from other countries' experiences. Britain also has the advantages of a centralized and widely accessible health care system and a relatively high level of trust in the authorities, she said.

But she warned that other nations have seen their virus cases increase quickly in a short amount of time, overwhelming some health services.

The prime minister conceded that the virus had the potential to be "a national challenge," but added that "we have the resources, we have got the health service, we have got the expertise to do it."

"I am very confident the British public understand that," Johnson said.

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Danica Kirka contributed to this story.