A record low number of emergency visits to hospitals across England were recorded in April as the population stayed away from emergency departments amid the outbreak.
The sharp drop has prompted concern that some people's conditions may have worsened as a fear of infection kept them from seeking care.
NHS England data shows 6,865 A&E attendances were recorded at Lancashire Teaching Hospitals NHS Trust last month.
That was 35 per cent fewer than in March, and a 50 per cent decrease from in April last year, when there were 13,681.
It reflected the picture across England, where accident and emergency departments were at their quietest for any month on record.
Nationally, there were 917,000 A&E attendances in April 2020, down 57 per cent from 2.1m in 2019.
NHS England said the fall was "likely to be a result of the Covid-19 response".
Dr Nick Scriven, a past president of the Society for Acute Medicine, said the drop in A&E attendances was "a significant concern" and people's conditions may have worsened as a result.
"This is a ticking timebomb in itself and it will be exacerbated by a myriad of other pressures in the coming weeks," he said.
"There will be an ongoing need to keep people with coronavirus separate from others to prevent transmission. Attempting to manage increased demand will be very challenging."
The NHS figures show emergency admissions at Lancashire Teaching Hospitals also fell, from 4,127 in April 2019 to 2,572 last month.
John Appleby, director of research and chief economist at the Nuffield Trust, said: "People are likely putting off seeking care because of Covid-19 infection fears and worries of burdening overstretched NHS staff; this is despite some reassurance from both the Government and the NHS that these services are open.
"We do not yet know what impact this is having on people's health – some people will have self-treated or sought other sources of care."
Professor Stephen Powis, NHS medical director, said although A&E attendances were sharply down, the majority of reductions were for lower-risk conditions.
"The NHS has launched a public information campaign reminding the people of the importance of seeking care for urgent and emergency conditions," he said.