Dangers of Legionnaire's disease

Legionnaire's disease is usually associated with contaminated water and air conditioning systems.

It is a common pneumonia, caused by the bug Legionella pneumophila in 90 per cent of cases.

L longbeachae is much less common, and outbreaks in the UK are sporadic - just nine cases reported since 1984. However, L longbeachae does have a much higher incidence in Australia, where compost carries a warning about the dangers of the disease. The bacterium can be found in potting mixes, compost heaps and in composted animal manures.

It generally infects the lungs, causing pneumonia. Symptoms include fever, coughing, breathlessness, chest pain and diarrhoea.

People of any age may be infected, although the disease is more likely to hit the over-50s and those with a weakened immune system.

Antibiotic treatment is the same whatever the organism causing the disease.