Legionnaires' outbreak prompts air-con alert

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The Auckland region has been hit by a sudden increase in reported cases of a potentially fatal lung infection, prompting a health authority to ask for urgent chemical treatment in all buildings with air-conditioning that relies on water cooling towers.

The Auckland Regional Public Health Service said it had been notified of nine cases of legionnaires' disease in the past six weeks. The region's average number of cases is typically one or two every six weeks.

Legionnaires' disease, a form of pneumonia, can be caught from the contaminated water cooling towers of large air-conditioning systems, domestic shower heads, spa pools, water blasting and soil, compost and potting mix.

The risk from large air-conditioning systems is potentially both to the building's occupants and to people on the streets exposed to contaminated, wind-borne water droplets.

The disease is caused by legionella bacteria, which can also cause the mild respiratory illness Pontiac fever. The bacterium can be spread by fine mists of contaminated water.

Because of the outbreak, the public health service, with the Auckland Council's help, is urging the owners and managers of buildings that contain an air-conditioning cooling tower, or industrial processes that use water and generate aerosols, to arrange immediate shock-dosing of these systems.

The people sick with legionnaires' disease are from all over the Auckland region. They are adults of all ages and none has died. Because of the long incubation period of the disease, it may not be possible to find the source quickly.

Medical officer of health Dr Simon Baker said that because of the severity of legionnaires' disease, it was important that building managers acted quickly, to avoid unintentionally causing more people to become sick.

A public health service investigation connected a 2006 outbreak of legionnaires' disease in the suburb of Beachlands, in which an elderly man died, to a water blaster at a nearby marina.

The water blaster was upwind, on the prevailing wind, of the homes of four people who caught the illness.

"Aerosols containing legionella discharged to air by the marina water blaster may have infected some cases directly or may have seeded roof-collected rainwater systems," public health physician Dr Greg Simmons and colleagues said in a report on that outbreak in 2007.

"Some cases may have been exposed by contaminated bathroom showers. Roof-collected rainwater systems need appropriate design, careful cleaning and the maintenance of hot water temperatures [in the tank] at a minimum of 60C to reduce the chances of legionella multiplying."

Home and vehicle air conditioners are not a source of Legionella bacteria.

THE RISKS

Legionnaires' disease:
* A form of pneumonia caused by inhaling water or soil contaminated with legionella bacteria.
* First symptoms include muscle aches, headache, tiredness, loss of appetite and coughing.
* Followed by high fever, chills and occasionally diarrhoea.
* Treatment: antibiotics.
* Around 80 cases a year of the disease and its milder form. Around three deaths a year.