LONDON — Up to one fifth of employees could be off work in Britain when the coronavirus outbreak peaks, the government said Tuesday as it outlined a new action plan. Britain so far has 39 confirmed cases of COVID-19, and Prime Minister Boris Johnson warned this was "highly likely" to increase. More than 3,100 people have died and over 90,000 have been infected worldwide. But the prime minister said: "For the overwhelming majority of people who contract the virus, this will be a mild disease from which they will speedily and fully recover." In a press conference with his chief medical and scientific advisors at Downing Street, Johnson unveiled the steps his government would take if coronavirus takes hold in Britain. These include asking people to work from home, reducing the number of large gatherings such as football matches, and shutting schools. "In a stretching scenario, it is possible that up to one fifth of employees may be absent from work during peak weeks," the plan says. The pressure on emergency services could see police concentrate on only the most serious crimes and hospitals both delay operations and bring retired healthcare staff back to work. But these measures will not be introduced until the outbreak is clearly established, and only then if experts assess the benefits outweigh the costs. The peak of the virus is expected to occur two to three months after the outbreak begins. "For the vast majority of the people of this country, we should be going about our business as usual," Johnson said. He said that hand washing with soap and water — "for the length of time it takes to sing "Happy Birthday" twice" — was the most effective way to prevent the virus spreading. "I continue to shake hands," he added. UK health officials say that in the worst case scenario, 80 percent of the population could become infected with coronavirus. Evidence from China, where the outbreak began, suggests a mortality rate of one percent, pointing to up to 500,000 deaths in Britain. However, this includes many variables and Chief Medical Office Chris Whitty said predicting numbers was "largely speculative". The risk was highest for elderly people and those with underlying health conditions. Children appear to be less affected than other groups, he added. — AFP