Four hundred and sixty cases of the coronavirus have been confirmed in the UK, with the biggest rise in a single day since the outbreak began.
Almost 27,476 people in the UK have been tested for the virus so far, with 460 found to be positive for the respiratory infection. Six people who tested positive have died.
These maps, charts and graphics that will help you understand the situation in the UK and how the authorities are dealing with it.
1. The number of UK cases is growing
The new coronavirus, which causes the respiratory disease known as Covid-19, was first confirmed in the UK at the end of January.
Since then, cases have been reported across the UK, with 83 new cases announced on Wednesday.
The figures show 387 of the confirmed cases are in England, 36 are in Scotland, 18 are in Northern Ireland and 19 are in Wales.
Hertfordshire has more cases of coronavirus than any other local authority in England outside London – where there are 104.
The capital saw an increase of 13 cases on Wednesday and all but two local authorities in London now have confirmed cases.
The start of the UK peak of the coronavirus epidemic is expected within the next two weeks, according to Dr Jenny Harries, England’s deputy chief medical officer.
But numbers for the UK are much lower than other European countries, such as Italy, for example, where there have been more than 10,000 cases and 631 deaths.
While there were a number of people testing positive throughout February, figures in the UK began to increase significantly at the beginning of March.
Prof Chris Whitty, the country’s chief medical adviser, said he was expecting the numbers to “increase initially slowly, but really quite fast after a while, and we have to catch it before the upswing begins”.
NHS England plans to expand the number of people it can test in a day to 10,000, up from 1,500.
Globally, authorities have confirmed more than 118,000 cases of the coronavirus and more than 4,200 deaths.
The vast majority of cases – more than 80,900 – are in China, where the virus originated in December.
2. We are in the first phase of the government’s response
The government has published its action plan for dealing with the virus, which involves three phases – contain; delay; mitigate – alongside ongoing research.
The emphasis is currently on the contain and research phases, but Mr Johnson says extensive preparations are being made to move to the “delay” stage to stop the wider spread of the virus.
While the containment phase involves catching cases early and tracing all close contacts to halt the spread of the disease for as long as possible, the delay phase could mean the introduction of “social distancing” measures, such as urging people to work from home – if possible – and cutting back on socialising.
Closing schools and banning big events is less likely to happen.
However, Professor Whitty said that within the next few weeks we could reach a stage when people with “even minor respiratory tract infections or a fever should be self-isolating for seven days afterwards”.
If the virus becomes widespread, the government may decide to enter the mitigation phase, when health services are asked to focus on critical care and retired NHS staff could be asked to return to work.
Mr Johnson said the government would announce further steps in the days and weeks ahead to help people “protect themselves, their family and in particularly the elderly and vulnerable”.
3. People who think they have coronavirus should contact NHS 111
If there’s a chance you could have coronavirus, you are advised not to go to a GP surgery, pharmacy or hospital.
Instead, the NHS says you should contact its dedicated 111 online coronavirus service if you are in England.
In Scotland, you should call your GP or NHS 24 on 111 out of hours. In Wales call 111 (if available in your area) or 0845 46 47. In Northern Ireland call 111.
As a result, you may be asked to stay away from other people (self-isolate). You may also be passed on to your local health protection team for testing.
Advice for people who have travelled back to the UK from the main affected areas and some other countries has also been issued by the government.
4. Some of the UK’s cases can be traced to Europe
Numbers across Europe have been increasing over the past week, as well as in the UK.
Many of the UK’s cases have been people who recently travelled from affected countries – including Italy and France as well as China and Iran.
Italy has been particularly badly affected and the UK government has advised all those who have developed symptoms after returning from anywhere in Italy – not just the north of the country – to stay at home.
Those returning from quarantined regions in Italy, including Lombardy and Veneto, are being told to self-isolate even if they do not show symptoms.