The Canterbury District Health Board is hoping to find the second source of a potentially fatal disease after an outbreak in the region.

Six people have been hospitalised with Legionnaires disease, a rare but potentially lethal strain of pneumonia, since April.

They've all since been discharged.

The first four people contracted the disease from an industrial cooling tower in Hillsborough which has been treated.

Now the CDHB's working to identify the second source, which infected the last two sufferers.

All six people have a connection with the industrial building, either working or living near it and health experts believe the second source must too be in Hillsborough.

Medical Officer of Health Dr Ramon Pink says the risk to the public is very low, with the last person affected at the end of May.

Nevertheless he says industrial companies in the area need to keep on top of cleaning and monitoring air conditioning and cooling ducts.

This strain of the disease is airborne and can be inhaled from air conditioning outlets.

The community needs to be alert, and anyone presenting influenza-symptoms like fever, muscle aches or headaches should contact a doctor.

Dr Ramon Pink says they're doing all they can to find the newest source, and are working with industry experts.

It's an unseasonable time to contract the disease, which is most common in summer months as it's often connected to gardening supplies.

Canterbury often has a high number of people struck by legionnaires, with 18 already affected this year.