The chief medical officer has warned the coronavirus will result in “some deaths” in the UK – as two more people in Scotland tested positive.
Chris Whitty, who also acts as the chief medical adviser to the government, warned of a “significant number” of cases of the illness, officially known as Covid-19, to come in the next six weeks.
He told Sky News it is "sensible" to plan for up to 20% of people to be sick at one time, while warning that some of those with the disease will die.
Further cases in Scotland
Officials were told overnight of two more people in Scotland testing positive for coronavirus, bringing the total testing positive in the UK to 53.
Scottish health secretary Jeane Freeman said she could not say yet if the new cases of Covid-19 were linked to the first one north of the border, in Tayside.
She told BBC Radio Scotland: "We now have three cases in Scotland.”
Professor Whitty said “community transmission” of coronavirus is likely to be happening already.
He told BBC Radio 4's Today programme: "It's when it's going from person to person to person and then we pick it up – that's what we mean by community transmission.
"It is likely that will be happening, if not now, but soon. I think it's likely to be happening at the moment, not definite.”
The government is launching a renewed public information campaign urging people to wash their hands to prevent the spread of coronavirus.
Adverts will seek to drive home the message that regular hand-washing is the single most important action individuals can take in the fight against Covid-19.
It comes the day after the government launched its "battle plan" to combat the outbreak with a warning that up to a fifth of the UK workforce could be off sick when the virus hits its peak.
The latest adverts – to be rolled out across print, radio, online and billboards – will reinforce the message that people should be washing their hands more often.
That includes when they come in from home or work, after they blow their nose, cough or sneeze, and before they eat or handle food.
The adverts say washing should be for 20 seconds, using soap and water or hand sanitiser.
Health secretary Matt Hancock said: "We all have a role to play in stopping this disease and that's what this expanded campaign is all about – making sure the public knows exactly what they should be doing to keep themselves and others safe.
"Washing hands regularly is the single most important thing that an individual can do."
NHS England has ordered hospitals to review their intensive care bed numbers and how they could be increased to cope with a surge in cases.
In a letter to NHS bosses, strategic incident director Keith Willett said a level four incident – the highest category – had been declared.
He raised the prospect that infected patients may soon start being treated on hospital wards as the numbers grow.
Hospitals have been told to draw up plans to segregate wards such as A&E departments in the event of a "significant escalation" in cases.
All adults and children in intensive care with any kind of respiratory infection must also now be tested for the virus.
Officials are still working to delay the peak of the virus until the warmer months, when health services are less busy coping with seasonal flu.