The coronavirus lockdown will have to remain in place for "several more weeks" scientists have warned as ministers appealed to public to stay at home for Easter.
Experts advising the Government on the crisis said the social-distancing measures introduced last month appeared to be working better than expected.
However they insisted there could be no relaxation of the restrictions until it was clear the peak of the epidemic was past.
The warning followed the announcement on Thursday that Boris Johnson had been discharged from intensive care at St Thomas' Hospital where he is being treated for the disease.
Downing Street said that he was in "extremely good spirits" and would be receiving close monitoring during "the early phase of his recovery".
With fine weather forecast for many parts of the country over the long bank holiday weekend, minister fear people may flout the rules and flock to beaches and beauty spots.
NHS England's national medical director Stephen Powis said it was "critical" that people obeyed the instructions and stayed at home.
"We are beginning to see the benefits of this social distancing. We do believe the virus is spreading less" he said.
"That will only continue to happen if we don't get complacent and continue to follow those instructions."
The warning came as the latest official figures showed the number of hospital patients in the UK who had died after testing positive for Covid-19 had risen to 7,978 as of 5pm on Wednesday – an increase of 881 on the previous day.
The Government is due to carry out the first three-week review of the lockdown measures next week.
Foreign Secretary Dominic Raab, who is deputising for Mr Johnson, has said the Government's Scientific Advisory Group for Emergencies (Sage) would be studying the evidence but they would not be to say more until the end of the week.
Professor Paul Cosford, emeritus medical director for Public Health England (PHE), said the while there were signs the spread of the disease was slowing, it was likely the restrictions would still be needed for several weeks.
"It really does look like the numbers are flattening. That is really important because that is the first sign that we may be getting to the peak of this pandemic," he told the BBC Radio 4 Today programme.
"I think several weeks isn't unreasonable. Let's hope its sooner than that. Just for now, we are getting on top of this but we have got an awfully long way to go and it is absolutely critical that we continue with all the actions that are required of us."
Professor Neil Ferguson of Imperial College, who was the lead author of a report which warned 250,000 people could die if the Government did not introduce social distancing, said the measures were working better than they had predicted.
"We made quite conservative assumptions about the level of contact reduction these measures would result in," he told the BBC Radio 4 Today programme.
"There is some preliminary evidence in terms of contact surveys, in terms of data from companies like Google about how people move, that we have seen even larger reductions in normal behaviour, contact, than we would have dared hope.
"That is good news but we have still got to see that reflected in case numbers coming down."
Prof Ferguson, who is a member of Sage, suggested when the time came the restrictions could be eased in stages, but said more testing would be needed to ensure the virus was kept in check.
"Without doubt measures will be targeted, probably by age, by geography, and we will need to introduce – in my view – much larger levels of testing at a community level to really be able to isolate cases and more effectively identify where transmission has happened," he said.
Prof Cosford suggested one of the first measures could be to allow schools to re-open.
"We do know that children are at very low risk of getting complications from this disease. The importance of children's education, children being in school, is paramount," he said.
"I could conceive of circumstances in which some of the restrictions are lifted sooner and some are lifted later."