Most of the victims are being treated at Hereford County Hospital

Seven new cases in the outbreak - which has killed one man - were confirmed on Saturday, bringing the total number of people affected to 22.

That marked the biggest rise in the number of cases over 24 hours since the outbreak began.

Health officials said that is not surprising as GPs were on the lookout for symptons of the disease.

They have stressed that it is still safe to visit Hereford, where work to decontaminate a cooling tower at a Bulmers cider plant is continuing.

In a statement the joint agencies fighting the spread of the disease said: "The new cases do not change the approach to tackling the outbreak which includes a rigorous case-finding exercise with mapping of patients movements, along with intensive investigations by the environmental health teams."

'Not unexpected'

The latest cases include six men, aged from their 40s to 70s, and one woman in her 50s.

All of the seven, along with the majority of the other infected patients, are said to be stable in hospital.

One patient, a man in his 70s, was said to have taken a turn for the worse on Friday night while another has been released after treatment.

Mike Deakin, the county's director of public health, said the latest cases were "not unexpected".

GPs were on the lookout for the disease and even those with the mildest symptoms were being diagnosed, he said.

These new cases may have contracted the disease from a local source but we are confident this has now been eradicated as part of extensive cleaning and disinfecting Dr Brian McCloskey, Health Protection Agency

'Increased lookout'

Mr Deakin said: "The procedures that have been put in place since the start of the outbreak mean that GPs are on increased lookout for Legionnaires' symptoms.

"We would emphasise again that Legionnaires' disease cannot be transmitted person to person, and that it is safe to visit Hereford."

Dr Brian McCloskey, of the Health Protection Agency, said the new patients had been diagnosed within the normal incubation period of Legionnaires', which is between two days and several weeks.

Mr McCloskey said: "This means that these new cases may have contracted the disease from a local source but we are confident this has now been eradicated as part of extensive cleaning and disinfecting."

The legionella bug was found in a sample taken by health officials from an evaporation tower at the Bulmers plant on 7 November but it has not been confirmed that this is the source of the outbreak.