In particular, the virus reproduction "R" number must be kept below one - meaning each infected person could expect to pass it to fewer than one other person on average. Outlining several key unknowns about coronavirus, Prof Whitty highlighted seasonality, saying: "There may be a seasonal element to this, we don't know, it's too early with this virus." Speaking at the daily coronavirus briefing Boris Johnson said the ‘R’ number will be the crucial factor in deciding how far to ease the lockdown. Chief Scientific Advisor Patrick Vallance revealed the national R number is now between 0.6 and 0.9 - while in London it is 0.5 to 0.7. But Prof Vallance and the Prof Whitty, both warned the R number must be kept below 1 to avoid overwhelming the NHS.

Source: Daily Mirror April 30, 2020 21:58 UTC