LONDON — The British government’s top medical adviser has warned that number of people in hospital with the coronavirus could reach “quite scary” levels within weeks as cases soar from the delta variant and the lifting of lockdown restrictions.

Professor Chris Whitty spoke on a webinar hosted by London’s Science Museum, saying the U.K. is “not out of the woods yet.” His comments came in the wake of government figures showing that coronavirus infections have struck another six-month high and the number of people in hospital with COVID-19 and subsequently dying are at their highest level since March.

There were 3,786 people in hospital with COVID-19 and another 63 virus-related deaths reported Thursday. Another 48,553 confirmed lab cases were reported Thursday, the biggest daily figure since Jan. 15. The government has stated that daily infections could hit 100,000 this summer.

At the height of the second wave earlier this year, some 40,000 people were in hospital with COVID-19 and deaths reached 1,500 people a day.