The NRC has a three tier status system for swimming water quality on the monitored sites, with green considered suitable for swimming, orange considered potentially unsuitable for swimming and red unsuitable for swimming.
"At sites that have had high levels of bacteria recorded, or where there is advisory signage present, we recommend against the collection of shellfish for 28 days from the time of sampling.
"We also advise people to not swim in the water or conduct activities that are likely to involve head immersion for seven days or until water tests show that it is safe to swim," she said.
Exposure to contaminated water can cause gastrointestinal illness (tummy upsets), cold and flu-like symptoms, and skin, eye and ear infections.
If you have concerns about your health as a result of the water quality in Northland beaches and rivers contact the on-call Health Protection Officer (09) 430-4100. For enquiries regarding the surveillance of Northland beaches and rivers, call 0800 002 004.
If water testing shows counts above the recommended guideline the relevant district council will put up a temporary health warning sign. Swimming at these sites is not recommended for seven days from the date written on the sign. The sign will remain in place for a further 28 days advising against shellfish harvesting as there is still a viral risk.
As of Friday six spots around Northland were red flagged and considered unsuitable for swimming: Kerikeri River at Rainbow Falls and Stone Store; Ahipara Beach off Kaka St; Omapere at Pioneer Walk Rd; Opononi Foreshore; Paihia's Te Haumi River mouth and Ruakaka River below the motor camp.
Before going for a swim, remember the four simple rules:
• Don't swim if there are warning signs indicating water is unsuitable for swimming.
• Avoid swimming two to three days after heavy rain.
• Don't swim if water looks dirty/murky, smells or it has scum on the surface.
• Be aware of potential sources of contamination nearby or upstream.
