Health officials throughout Europe and beyond have been trying to slow the speed of the coronavirus pandemic.
Many have introduced tough "social distancing" measures to keep people apart.
But with bars and restaurants still open in the UK, is London behind the rest of Europe in terms of reacting to this crisis?
'You must be a fast mover'
The World Health Organization (WHO) Executive Director, Dr Michael Ryan, has warned that a lack of fast action can lead to severe consequences.
"The lessons I've learned after so many Ebola outbreaks in my career are: be fast and have no regrets. You must be the first mover. The virus will always get you if you don't move quickly," he said in a press conference.
What is 'flatten the curve'?
One graph has been consistently used to show why acting fast and slowing the pandemic peak is crucial. It has been coined "flatten the Curve", and compares when measures are taken against when they are not.
When key measures are not taken, such as social distancing, limiting large gatherings and correct hand washing, the peak of the pandemic happens quickly - with the number of cases far exceeding the capacity by which a health system can cope. When control measures are in place and adhered to, the peak is spread over time, reducing the burden on healthcare systems.
Why is social distancing so important?
"I can't stress enough how important it is to flatten the curve and to do so immediately," Dr Ciara Kelly, an Irish physician and radio presenter told Euronews. "There is no health service in the world that is capable of dealing with the influx of patients that we expect coming in the here and now with coronavirus".
"The reason flattening the curve is so important, is that if you flatten the curve, you give health services a fighting chance of helping people and of saving lives," Dr Kelly said. Slowing the acceleration of the number of cases will allow health services to cope better, allowing "more lives to be saved".
"The virus, COVID-19, is spread person-to-person," she said, noting that it is contracted by being in contact with an infected individual's "droplet spread", which is emitted upon coughing or sneezing, or touching infected surfaces. "If you can engage social distancing actively, you can save lives. If you don't come in contact with the virus, you can't catch the virus."
"It's not easy for all of us to stay home alone - it's quite challenging. But it is our only defence against a virus that we have no immunity to, that we have no cure for and we have no vaccine for," Dr Kelly said, warning against lax social distancing.
Should there be coherence in policy?
"Throughout Europe, we are seeing levels of contagion we did not expect. All of Europe needs to pull together to see that of our safety is in each other's hands," Dr Kelly said.
While Italy and Spain are among the countries that have enacted strict quarantine measures, the UK hadn't put forward any social distancing regulations before Monday afternoon. Prime minister Boris Johnson did tell people to avoid offices, pubs and social gatherings, but stopped short of closing restaurants, bars or schools down.
Measures introduced by the UK were taken days ago by other countries, including Ireland, Denmark and Austria.
Responding to this, Dr Kelly called for a coherent pan-European strategy.
"It is vitally important, because we live all in countries next to each other, that we are all on the same page with regards to social distancing. I can't say it more clearly, that the UK is an outlier in this respect," said Dr Kelly, speaking before Boris Johnson's speech on Monday.
"My personal view, as a physician, is that they are placing the economy ahead of the lives and of the health of their own citizens. But their citizens put all citizens of Europe at risk, including on my own island of Ireland, because Northern Ireland is behaving differently to the Republic of Ireland".
"Currently, the UK strategy is a danger to their own citizens and to the rest of Europe".
What has worked so far?
Taiwan, Singapore, and Hong Kong have curbed their number of cases through contact tracing, a high degree of testing and social distancing - measures that have proven instrumental, showing preparedness following outbreaks of SARS in 2003 and N1H1 in 2009. Although alongside China, Taiwan has reported just one death at the time of writing.
"If we flatten the curve now, this won't be forever, we will get through to the other side of this. Antivirals will come, the vaccine will be developed and we will be in a different place. But these are the critical weeks".