Legionnaires Disease – Warning, take precautions with compost!

Compost is a good fertiliser with major benefits for the soil, fruit and vegetables and for human nutrition. However, everyone should be aware that compost (and potting mix) contain bacteria that cause Legionnaires Disease.

Legionnaires Disease is a form of bacterial pneumonia that can cause the lungs to be overwhelmed with infection, causing hospitalisation and potentially death. Throughout the world, Legionnaires Disease has been under-diagnosed, partly because it rapidly becomes a medical emergency requiring a rapid response. In NZ, there are approximately 200 cases of Legionnaires every year, most of it caused when people inhale dust from compost or potting mix. About one-third of cases are admitted to intensive care and about 11% actually die from Legionnaires Disease.

Any person of any age can become infected. It is entirely preventable if people wear dust masks, protective clothing, gloves and wash hands frequently and carefully. A good hand wash should be at least 20 seconds under running water (not a quick flick). Also if tons of compost are being spread mechanically, it will create dust so best to keep well clear of any spreading equipment and take precautions to let the dust settle before allowing anyone back into the area.

There has been some newspaper publicity about this recently and there will be more as we publish more about it, but because infections tend to be seasonal, there is a lack of attention to it. (The seasonality is because people tend to use compost and potting mix in spring and summer.)

The Living Earth company do know about this and they have warning notices in small print on their compost bags. But most people are not aware of the risk and how to avoid it and it’s something positive we can do for WIG members if we can educate people to the risks and how to manage them. Particularly those interested in organics.

Ian Sheerin

Retired Doctor in Public Health, Christchurch School of Medicine.

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New Zealand Walnut Industry Group