A gardener contracted a rare case of legionnaire's disease through a cut in his hand while handling compost, British doctors report.

The incident is rare, but the U.K. Royal Horticultural Society has issued warnings about the risk of contracting legionnaire's disease from handling compost, and has announced that bags of potting compost will carry warnings, the paper in Friday's issue of The Lancet said.

Legionnaires' disease is a type of pneumonia that is caused by legionella, a bacterium found mainly in warm-water environments. Symptoms include high fever, chills and a cough.

Dr. Simon Patten of Royal Alexandra Hospital in Paisley, Scotland, described how the 67-year-old man, who has previously fit, came down with a serious fever in March.

When doctors examined him in hospital, he had an eight-day history of fever with trembling, confusion, lethargy, and shortness of breath.

The man had a high temperature and signs of pneumonia in his left lung on X-rays.

"We treated our patient with oxygen, intravenous fluids and antibiotics, but his respiratory function deteriorated, necessitating transfer to the intensive care unit for intubation," Patten and his co-authors wrote.

"When we questioned the patient to find out the source of this infection, we discovered that he was a keen gardener and had lacerated his left index finger two days before the onset of his symptoms, while planting with compost," they wrote. "We presumed that this cut was the site of entry of the organism."

A range of tests, including a urine test for legionella bacteria, were negative.

A more invasive test of his lungs tested positive for Legionella longbeachae, a rare form of legionella that can't be detected in urine samples.

Treatment with the antibiotic levofloxacin improved the man's condition, and he was discharged to a regular respiratory ward seven days later, before being discharged.

The man was well at follow-up in May 2010.

About 90 per cent of legionnaire's disease are cased by Legionella pneumophila.

Cases caused by L. longbeachae are much less common, with nine cases reported in the UK since 1984. Higher incidences are found in Australia, New Zealand and Japan, the authors said.