Traces of the Legionella bacterium have been found at a hospital already in the midst of a viral outbreak.

Officials at Perth Royal Infirmary said one member of staff fell ill with suspected Legionnaires' disease but is now recovering.

On Wednesday it was revealed that two elderly people, who were already seriously ill, died after a viral infection which struck patients in the Tay ward, a geriatric ward in the hospital.

Legionella was discovered in non-patient areas

Twenty one people were initially affected but the hospital has now confirmed that a further nine people in a general medical ward have been taken ill.

Seven people in the geriatric ward are still suffering from the virus.

The traces of Legionella were found in three areas of the hospital after routine testing.

Dr Drew Walker, the trust's director of public health, said small traces of the bacteria were found in sluices - side rooms used for waste disposal.

They are areas used only by staff.

There is no risk to patients from legionella NHS Tayside

He added that there was no evidence the infected staff member had been near the sluices and the illness appeared to be "coincidence".

Dr Walker said: "There is no risk to patients from Legionella being found in sluices because patients do not go into these areas.

"Measures to remove the infection are well understood and are known to be effective.

"The discovery of Legionella demonstrates that our monitoring and control procedures are working properly."

One health care worker from the hospital was understood to have acquired the infection and is now recovering at home.

The general medical ward where nine patients were taken ill has been closed to new admissions.

Relatives have been asked to keep patient visits to a minimum.

Water sources

An outbreak control team was formed when the outbreak came to light.

Legionnaires' disease, which is also known as Legionellosis, is a rare form of pneumonia.

It is most often contracted through inhalation of moisture from water sources like whirlpool baths, showers, and air cooling systems contaminated with Legionella pneumophila.

The disease can most often strike those with an existing health problem, the elderly and smokers.

It was first identified in 1976 after an outbreak among members of the American Legion, an ex-servicemen's organisation, attending a conference in Philadelphia.

The symptoms include diarrhoea, vomiting and stomach cramps and usually improve within 48 hours.

Legionnaires' is most often treated with the antibiotics and recovery often takes several weeks.