Managers in an NHS area are considering using "field hospitals" to deal with the surge in patients.
Sarah Whiteman, chief medical director of the Bedfordshire, Luton and Milton Keynes Integrated Care Board told colleagues the use of tents was a "real possibility".
In an email, she also asked colleagues to sign temporary contracts to work in emergency departments.
The board said the use of tents in hospital grounds was not imminent.
Dr Whiteman's email, obtained by The Sunday Times and seen by the BBC, began with the statement: "Call to arms".
It emphasised how busy the acute units were within her board's operational area, including Bedford, Milton Keynes and Luton and Dunstable Hospitals.
In the message, she promised staff would receive training and induction if they stepped forward to support colleagues.
Emergency services at the region's hospitals have seen a surge in the numbers of people presenting with Covid and flu symptoms.
Approximately one in eight beds in England is now occupied by patients with these infections.
Milton Keynes University Hospital said it had seen an "unprecedented" number of patients attend its emergency department, with a patient arriving every four minutes over a 24-hour period at one point.
A spokesman for Bedfordshire, Luton and Milton Keynes Integrated Care Board said: "Health services across Bedfordshire, Luton and Milton Keynes are experiencing unprecedented demand.
"In response, we have been working with partners to consider as many options as possible to ensure local people get the care they need.
"One of these options is to create temporary field hospitals to rapidly increase bed capacity. There are no plans to deploy temporary field hospitals imminently."
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