Four elderly residents at the same care home have died after showing coronavirus symptoms, a council said.
A fifth person without symptoms has also died at Harry Sotnick House in Portsmouth, Hampshire.
A number of other residents who also may have Covid-19 are being cared for in isolation within the home, Portsmouth City Council said.
Council leader Gerald Vernon-Jackson said the home was being used by the council to relieve pressure on the NHS.
Two of the deceased were recently admitted to the Hampshire County Council-run home from hospital, but Mr Vernon-Jackson said he did not know if they were moved under the scheme to relieve Portsmouth's Queen Alexandra Hospital.
Three of those who died were existing residents.
The city council said there had been no testing for Covid-19 of those who had died as guidance stated tests should not be used if there will be no change to the care given.
"It's incredibly sad for everybody, the families and for the people who work there," Mr Vernon-Jackson said.
"I think that's becoming clear as this goes on in France, Spain and Italy, one of the areas most at risk is people living in care homes and nursing homes."
He said personal protective equipment (PPE) was a "real problem" for the 39 care homes in the city.
"The stuff that was meant to arrive at the weekend from the Government did not.
"When I've talked to people working in care homes they have been really worried because they are running out or have run out."
The council said it did not know how many people were currently being cared for at the 92-bed home and it was working with Public Health England (PHE) specialists over the outbreak.
The home has been deep-cleaned and care workers are still working under the guidance of PHE, he added.
It has been closed to visitors since 22 March.