Between January and June this year, 163 cases of Legionnaires’ disease were reported in England and Wales – 26 per cent more than in the same period in 2006.

Clusters of infection have been found in London, the Midlands and South West England.

Dr Carol Joseph, a HPA expert in Legionnaires’, said: ‘We’ve investigated and not yet determined a common link.

‘There’s a mixed bag of reasons for the increase.’

Spread of the disease can be linked to the weather – the bacteria are carried in water and spreads when converted into an aerosol.

High temperatures in April were accompanied by a rise in cases of Legionnaires’. A big rise was also seen in June and is expected for July, said Dr Joseph.

‘We’ve got no evidence yet that the floods have had any effect.’

But Dr Joseph said there are concerns that cooling towers switched off during the heavy rains in June and July could be a breeding ground for the bacteria if they are not properly sterilised before being switched back on.

In Surrey, the HPA is also investigating a case of Legionnaires’ disease that has been linked to the Institute of Animal Health in Pirbright. It follows scrutiny on lab containment procedures following the recent foot and mouth outbreak.

Dr Joseph said GPs ‘should be highly suspicious of people who’ve come back from holiday who have a pneumonia type illness and a suntan’.

But given that two-thirds of Legionnaires’ cases detected in the first half of 2007 were contracted in the UK, distinguishing Legionnaires’ from other flu-like illnesses could be difficult.

Dr Joseph said GPs should refer patients with suspected Legionnaires to hospital for a urine test.

Legionnaires’ typically affects people over 50 and presents as ‘flu-like’ symptoms with muscle aches, tiredness, headaches, dry cough and fever. Diarrhoea can also occur and confusion develop.

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