‘Gardeners’ disease’ might be a better name for it, but it’s known as ‘Legionnaires’ disease’ because in 1976 it killed 25 members of the American Legion (an organisation for armed forces’ veterans) who’d been at a convention.

We now understand it’s a form of pneumonia caused by a bacterium found in water: in the original case (and others since), water in an air conditioning system’s cooling tower. In New Zealand, however, a much more common source of infection is gardeners’ potting mix. You may have seen the warnings on the bags.

Whatever it’s called, it’s nasty. Every year more than 20 people are admitted to Christchurch Hospital seriously ill and found to be suffering from Legionnaires’ disease. Experience suggests 5-10% of them will die.

“It’s difficult to diagnose,” says Professor David Murdoch, in-coming Dean, and Head of the Department of Pathology at the University of Otago, in Christchurch. “The symptoms are similar to other forms of pneumonia, but Legionnaires’ disease doesn’t respond to the first-line antibiotics normally used.”

“What was curious,” he says, “is that we were finding more people in Canterbury contracting the disease than elsewhere in the country. As many as 20% of those admitted to Christchurch Hospital with pneumonia in spring and summer turned out to have Legionnaires’ disease; a much higher percentage than elsewhere. Colleagues suggested it must be something to do with Christchurch being the garden city!”

No, it wasn’t that. In part it was because, in the Canterbury health system, there was well-established interest in respiratory problems. In 1990, Dr. Ian Town1 , with the support of colleagues, established the Canterbury Respiratory Research Group. The group undertook a broad range of clinical research—into asthma, COPD2 , pulmonary embolism and pneumonia—including some of the early work on Legionnaires’ disease.

In part, it was because Canterbury Health Laboratories—the place that does the diagnostic testing—is, according to Professor Murdoch, “An excellent facility, as good as any laboratory I have seen around the world.”

Mainly, however, says Professor Murdoch, it’s because “Christchurch is the perfect place to do applied health research. The population is not too big, not too small. There is only one DHB, which makes things much easier than in other places, and in particular it’s because there is such a close interface between those in academia and those on the clinical side. Everyone’s committed to improving patient care and everyone just… gets on. It seems too grand to call it ‘collaboration’, because these are just the people I work with. Which institution employs us doesn’t really come into it: I’m at the University of Otago, but I use a CDHB email address and I also work at Canterbury Health Laboratories.”

This interest in respiratory infections, this excellent diagnostic laboratory and this Canterbury culture of working together, led to the awareness that Legionnaires’ disease is common in Canterbury and also led to better ways to use laboratory tests to diagnose the disease. In 2014, Professor Murdoch received funding from the Health Research Council of New Zealand to look at the prevalence of Legionnaires’ disease nationally. Early indications are that the disease is just as common elsewhere, including some areas where it has been only rarely diagnosed.

As you would expect, there is considerable interest in the research, nationally and internationally because better diagnosis of Legionnaires’ Disease will save lives. As Professor Murdoch points out, however, it remains a preventable disease: “We are working with the industry,” he says, “but gardeners should follow the advice on the compost and potting mix bags. Avoid inhaling the dust. Don’t work in unventilated places such as closed sheds and greenhouses. Open the bags away from your face. Use a facemask. And wash your hands afterwards.”

Professor David Murdoch, in-coming Dean, and Head of the Department of Pathology at the University of Otago, Christchurch.