Non-urgent planned operations in Cornwall and the Isles of Scilly are to be postponed for at least three months, health bosses have said.
The NHS Kernow Clinical Commissioning Group (CCG) said the move was to ensure "we have as many beds available as possible" for respiratory problems when coronavirus infection numbers peaked.
Routine referrals from GPs and most outpatient appointments were also to be postponed from Monday, it said.
Cornwall has seen five Covid-19 deaths.
The CCG said it knew "many people waiting for treatment will be disappointed or worried" but that staff would be "contacting everyone affected as soon as possible".
Urgent and emergency cases and cancer treatments would be "carrying on as normal" and some services could also be delivered through video and telephone consultations "when it is clinically appropriate", it added.
"We are sure our patients and local people will understand the need for the steps we are taking and support our staff over coming weeks and months", the CCG said.
Four of the deaths were patients over the age of 70 with underlying health conditions, Cornwall Council said.
They died at the Royal Cornwall Hospital, near Truro, over a five-day period.
The fifth death was announced by Public Health England on Sunday afternoon.
Cornwall Council confirmed it was a patient in their 60s also with underlying health conditions.
"Their family has been informed about the cause of death and are following national guidelines," it said.