Extensive investigations have so far failed to find any evidence that the cases of two people from Shropshire and a man from Powys are connected.

Health bosses today revealed a fourth patient was admitted to the RSH suffering from the disease on Thursday, but said the infection had been contracted overseas.

Paul Coulter, 46, of Whittington, near Oswestry, Graham Williams, 53, of Montgomery, and a third man from the Whitchurch area, who has not been identified, are all showing signs of recovery at the hospital.

Preliminary tests on samples of environmental water from sources such as cooling towers near where the three patients live and work have all produced negative results.

Dr Rob Carr, consultant in communicable disease control with the Health Protection Agency, said: “Our investigation is ongoing, but all the preliminary results would appear to indicate that there is no evidence of a common source of legionella infection such as would pose a threat to the health of the wider community in north Shropshire.

“We are now cautiously optimistic that these may have been isolated cases.

“But we will keep looking until we are absolutely certain that there is no single source of these illnesses,” he said.

Dr Carr added that the fourth patient spent a lengthy period out of the country and was abroad during the incubation period for Legionnaires’ Disease, so they were satisfied that the infection was not acquired locally.