Spring gardening warning as Legionnaires threat lurks

The South Island recorded the most Legionnaires' disease cases in the country over the past year, as health officials urge gardeners to wear masks and gloves when handling potting mix this spring.

Health NZ figures show 54 of the 152 legionellosis cases notified nationwide between September 2025 and August 2026 were in the South Island, and 46 of those people were hospitalised.

Across the country, 135 people ended up in hospital with the disease.

National Public Health Service medical officer of health Dr Matthew Reid said gardeners could take simple precautions to protect themselves.

"To reduce the risk of breathing in legionella bacteria only handle potting and compost mix bags outdoors or in well-ventilated areas, and open them carefully and away from your face.

"It's also important to wear gloves and a well-fitting face mask. An N95 mask is best."

Reid said N95 masks could generally be bought at DIY and gardening stores or local pharmacies.

"It's also recommended you dampen down soil products to reduce dust, and to wash and dry your hands thoroughly after gardening or handling potting mix."

Legionnaires' disease is a type of pneumonia caught by breathing in legionella bacteria, which thrive in moist environments and stagnant water, including potting mix, compost and other soil products.

Not everyone who breathes in the bacteria becomes unwell, and some people develop only a milder illness called Pontiac fever.

However, Health NZ said people aged over 50, smokers, and those with chronic illnesses or weakened immune systems were more susceptible and should be especially careful in the garden.

Reid said the symptoms were similar to a flu-like illness.

"[They] can include a cough, fever, chills, shortness of breath, muscle aches, headaches, nausea and vomiting, stomach aches, diarrhoea and excessive sweating. Some people also develop mental confusion or disorientation."

The illness typically worsens over several days and requires antibiotic treatment, with most cases needing hospital care.

"If you experience these symptoms, particularly after using potting mix or compost, you should contact your usual health care provider for advice or call Healthline for free on 0800 611 116."

The South Island region covers Nelson-Marlborough, Canterbury, South Canterbury, the West Coast, Otago and Southland.

The Northern region, which covers Northland and Auckland, was close behind with 49 cases and matched the South Island's 46 hospitalisations.

The Midland region, which includes Waikato, Bay of Plenty, Taranaki and Tairāwhiti, recorded 38 cases and 32 hospitalisations. The Central region, stretching from Hawke's Bay to Wellington, had 11 cases, and all 11 of those patients were admitted to hospital.