The University Hospital of North Staffordshire said the other patients were in a "stable or improving condition".
The Health Protection Agency (HPA) said it was continuing to work with the NHS in Stoke and the city council to identify any sources of the disease.
It said the outbreak was not hospital related and it was safe for patients.
Professor Harsh Duggal, Director of the Health Protection Agency's Health Protection Unit in Stafford, said: "We have been able to obtain detailed information on the movements of those affected.
"We are now working with HPA experts in mapping the outbreak and our partners to pinpoint possible sources, using the information we have gathered."
Professor Duggal said he expected to get more cases "over the next week or so" because of the incubation period of the disease.
Officials have said early signs include flu-like symptoms, with muscle aches, tiredness, headaches, dry cough and fever which can lead to pneumonia.
Diarrhoea and confusion may occur, as well as chest and breathing symptoms. The disease can be effectively treated with antibiotics.
A man is in a critical condition after the number of cases of Legionnaires' disease in Stoke-on-Trent reached 11.