Media playback is unsupported on your device Media caption Gardening is a healthy hobby but there are risks, says Dr Donaghy

Gardeners are being warned to wash their hands after using compost following a series of Legionella cases in Scotland over the past five years.

One man has died and five others have become ill after contracting a rare strain called 'Legionella longbeachae', which appears to come from compost.

The unusual strain is well known in Australia and New Zealand, where bags of compost carry warning labels.

But these are the first cases linked to compost to be confirmed in the UK.

As many gardeners head out to their gardens and allotments to enjoy the warm weather, experts are warning them to wash their hands after using compost, particularly before eating or smoking.

Take steps

"Gardening is a very healthy hobby but like anything in life there's a few risks," said Dr Martin Donaghy, medical director of Health Protection Scotland.

"Over the past five years we've had three confirmed cases of Legionella longbeachae, plus two 'probable' and one 'possible' so we do need to take steps to reduce the risk even further."

Doctors all over the UK are being urged to be alert for a link with gardening if they see patients with unusual pneumonia.

Symptoms of Legionella longbeachae include headaches, diarrhoea or a dry cough followed by pneumonia.

Most people recover after treatment with antibiotics and Dr Donaghy said other cases may have gone unreported.

"One of the features of this phenomenon is that we've only seen it in Scotland," he said.

"We're working closely with colleagues in England to find out the reasons for that.

The exceptional rarity of these cases would seem to indicate that any associated risks are exceedingly minimal Growing Media Association

"Are our services better at picking it up, or is it something to do with the nature of compost up here?

"We've got no evidence it's anything to do with the compost so we think it's more to do with being better at picking it up."

Like all forms of Legionnaire's disease, longbeachae is transmitted via very small droplets of water in the air.

All those who have contracted the illness so far were very keen gardeners, using different brands of compost.

Specialists are now investigating whether recent changes to compost formulas might be to blame as manufacturers move away from traditional peat-based growing media.

Global analysis

Health Protection Scotland is in discussions with the Scottish government on whether Australian-style warning labels should be recommended to manufacturers.

A spokesman for the Growing Media Association said: "Since 1990, of the 12 reported cases of Legionella potentially connected to the longbeachae microbe in Great Britain, only three are thought to be related to gardening.

"In the same period, the UK public has used well over a billion bags of compost.

"The exceptional rarity of these cases would seem to indicate that any associated risks are exceedingly minimal."

The spokesman added: "Nevertheless, the growing media industry is committed to acting in a responsible manner on this important issue and is therefore conducting a detailed global analysis of the situation.

"For the moment, appropriate precautionary/hygiene measures are unclear, an observation supported by Health Protection Scotland."

A spokesperson for the Association of Organics Recycling added that compost is routinely heated to at least 60C for 48 hours as part of the manufacturing process, which is considerably hotter than the preferred temperature for Legionella bacteria.