Boris Johnson has announced the government's coronavirus masterplan - as medics hunt for anyone who came in to contact with Kent's first case.

The Prime Minister held an emergency COBRA meeting yesterday hours before the first case was confirmed in Kent.

The briefing was to discuss the outbreak but on its conclusion Mr Johnson only announced the threat was "likely to become more significant" and the country was "very, very well prepared".

Downing Street revealed its strategy for dealing with the respiratory condition, now known as Covid-19, which has killed 3,000 and infected 90,000 globally, just before 11am.

Worst case projections show up to a fifth of workers could be off work at the same time, while army medics and retired health professionals could be drafted in and non-urgent surgery delayed.

Schools could be closed and events cancelled, while people could be urged to cut unnecessary travel. Police forces would move to only focusing on the most serious offences if officers are off sick and the tax man may go easy on businesses hit financially by the outbreak.

Mr Johnson said he "fully understood public concern" but for the most part the virus was "mild".

"Keeping people safe is the government's priority," he said, adding: "We will make sure the NHS gets all the support it needs."

He reiterated the advice that people should sing Happy Birthday twice while washing their hands to ensure all germs are wiped out.

He added it is too early to say how many people may contract Covid-19, although no more than 80% of the population will be infected, England's chief medical officer prof Chris Whitty said.

Prof Whitty also said it is not possible to say with certainly how many people have caught and recovered from Covid-19 as sometimes symptoms do not present themselves.

There are plans afoot to delay the virus' peak as long as possible and push it to a time of year when the NHS is not already battling normal flu cases.

Wales' chief medical officer Dr Frank Atherton said "best guesses" suggested a peak of the virus between May and June, sparking fears GCSEs and A-Levels could be at risk.

Exam board watchdog Ofqual said: "We are working closely with awarding organisations and the Department for Education to consider how to manage any particular risks to the smooth running of exams and assessments should there be a widespread outbreak of coronavirus.

"We will update our existing guidance to reflect any specific arrangements schools and colleges should put in place if required. In the meantime, students, schools and colleges should continue to prepare for the summer exams and assessments as usual."

Health Secretary Matt Hancock had previously warned it was "inevitable" things would get worse and did not rule out cordoning off entire cities Wuhan-style.

In the UK more than 50 people have tested positive for Covid-19 but more than 13,900 have been tested.

Medics are now seeking to track down anyone who came in to contact with those diagnosed with the virus, with new cases also reported in Devon and Hertfordshire.

Yesterday in the wake of the announcement a member of staff at a business at Maidstone Studios had tested positive a grammar school in Faversham told parents students were in self-isolation after a family member was diagnosed.

Any students who came in to contact with them were seeking medical advice while a student at North Kent College was also sent home.

The fatality rate is 1%, compared to influenza's 0.1%, but that is greater for the elderly and those with pre-existing conditions and lower for younger people. Nearly 50,000 have recovered from Covid-19.

In Kent, following yesterday's news supermarket shelves were cleared of anti-bacterial hand gel as people went in to panic mode but Public Health England has advised washing with soap is just as effective.

Symptoms of Covid-19 include fever and respiratory symptoms including coughing, sneezing, and shortness of breath. The current evidence is that most cases appear to be mild.

If you have returned from at risk areas, including parts of Northern Italy, Iran and China, since February 19 you are advised to contact NHS 111. More information is available here.

Meanwhile Kent County Council chiefs have moved to reassure people they are ready to deal with the outbreak.

Cllr Roger Gough, the leader of the council, said contingency plans were in place to deal with an escalating crisis and increase in people contracting the virus. Those plans included the possibility of staff working from home as well as the prospect of pupils being asked to stay away from school.

He said: “At the moment, we are in a situation where we are simply seeking to monitor what is happening within Kent as a whole and responding to any localised events.

“We are in close contact with our schools and schools have come to us for advice when particular situations have arisen.”

On the possibility of staff working at home, he said: “There is nothing that has changed in terms of how our staff work at this point but clearly there could be. If we have a situation where someone was required to work at home, then clearly that [contingency plans] would kick in.”

The council recognised those who relied on services would be concerned but measures were in place to limit the impact.

He said: “We have extensive business continuity plans, which have been in place for quite some time; they are very important to all our staff, particularly those with public-facing roles and that is something on which we have done a great deal of preparation.”

Last month KCC had to shut down and deep clean two rooms at County Hall after a coronavirus scare, but the individual involved got the all clear.

Cllr Rob Bird, opposition Liberal Democrat leader at KCC, said: “We are getting warnings that it could become quite serious. KCC like any other organisation will have to ramp up its emergency plans.

“The problem with this virus is that you never know what is going to turn up and it could happen very quickly. KCC is aware of the challenge but there is still work to be done.”

Dealing with an outbreak will be co-ordinated by the Kent Resilience Forum.

It publishes and updates a risk register and outlines contingency plans for a range of events - including the possibility of a flu pandemic.

Recently, it was in the spotlight over the contingency plans for Brexit.

Implementing those plans falls to different organisations who work together; notably the NHS, local councils and the emergency services.

However, the detailed plans and the measures that could be taken are not published in detail.

To keep up-to-date with all the latest developments with your local hospitals and other health stories, click here.