That's probably the way two Beachlands men became infected with the pneumonia-like illness. Inhaling water mist or spray allows the bacteria into the lungs, and both men had the bacteria in their shower systems, Auckland region medical officer Dr Greg Simmons says.

He says the bacteria can't tolerate a water temperature of 55 degrees celsius or more but can live in temperatures below 50 degrees. "It likes warm water," he says. Dr Simmons says "It's not such an issue" with gas systems because they tend to boil the water before mixing it with cold. The bacteria is unlikely to survive in cold water because it becomes dormant in anything under 20 degrees celsius.

Other steam sources, such as spa pools, have the potential to pass the bacteria to humans, but Dr Simmons believes that this is unlikely in these cases. Although investigations into the Beachlands incidents are continuing, DR Simmons believes the two infections are isolated cases. He says the legionella bacteria was found in three rain tank systems close together. Tests on nine other household tank supplies in the area showed no bacteria.