The Covid-19 alert level will be raised to five – the highest setting, Government sources have said. Risk levels are measured by a five-level, colour-coded alert system - with 5, red, being the most serious.
It means experts consider there is a "material risk of healthcare services being overwhelmed" and there should be "extremely strict social distancing".
It is set by the Joint Biosecurity Centre, which includes all four nations' chief medical officers. The COVID-19 alert level refers to the threat of the epidemic and is separate from the tiering system in England.
It means that scientists consider virus so widespread that it risks overwhelming the NHS and that drastic action must be taken.