He said it was tricky sometimes to pinpoint if an infection had come from a particular business, and some were not formal businesses either - one of the deaths occurred after the victim received a traditional tattoo done with a bone.
"A lot of it would go unreported," he said.
"For every complaint we get, there might be 10 infections."
The RPH report focused on a survey carried out over 57 nail and beauty salons in the region in 2017, and showed many operators had little understanding on how easily infection could be transmitted.
"A lack of knowledge and inadequate infection control is prevalent amongst the nail industry," the report said.
"A significant portion of salons hire staff that have no formal qualifications, and ongoing training is not the norm."
Despite this, an "overwhelming" 93 per cent of surveyed salons were in favour of a bylaw being put in place to make the industry safer.
The bylaw would cover businesses where there is no regulation currently. It would not apply to health-care facilities, registered medical practitioners, registered acupuncturists, or pharmacies as these services are already subject to industry and professional standards.
"Unlike many countries there is no law in New Zealand that regulates the appearance industry. It is up to councils to set minimum standards in regulations that apply to the businesses operating in their local authority," Bentley said.
"While many businesses have good policies and practices to prevent clients getting infections or cuts, others do not. In some situations operators are not aware that the way they have been doing things is no longer best practice and potentially puts people at risk.
"We need to look at setting standards that protect customers so they can feel confident in the services they are purchasing."
Bentley and his team dealt with about one complaint per year, though he believed there were many more unreported.
"You can't categorically state that you picked that infection up from that activity," he said.
Some fixes were straightforward and just required education.
One of his officers visited a waxing salon after a skin infection complaint was made. They identified the problem came from using a stick to apply wax, and continuing to dip the same stick into the wax pot, then putting away the leftover wax to be used on the next customer.
"The simple fix was maybe a smaller tub that you fill up that should be sufficient to do one customer," Bentley said.
The bylaw would also outline a licensing process involving inspection and certification by council's environmental health team.
"It gives us the opportunity to go in proactively, perhaps on an annual basis," he said.
Council's principal policy advisor, Graham Sewell, said they wanted to be "proactive" in stopping infections before they started.
He said the bylaw was now in "pre-consultation phase", where council would go out to affected businesses to get their views on it.
"It's very much just gathering information," he said.
"What are your concerns, are these the right areas of the bylaw that should be addressed?"
If the proposal went ahead, it would take some time for the bylaw to be put in place, and it would not happen this year.
The pre-consultation phase is running until the end of May, and will allow council to consider feedback before drafting the bylaw, which would then be formally consulted on.
The survey findings
• Salons with an adequate number of trained staff were twice as likely to ask clients about pre-existing health conditions
• There is limited understanding of blood-borne viruses and other infections and how they are spread or controlled
• Staff are often not vaccinated, or their immunity status is unknown
• Some salons continue to use heel blades to remove calluses or hard skin, which is associated with a high risk of cutting the underlying tissue and bleeding
• The majority of salons have no written infection-control protocols, or cleaning schedules
• While 21 per cent of salons were adequately disinfecting and sterilising equipment, half of them failed to store or treat the equipment in such a way as to prevent recontamination
• Slightly less than half of salons had an adequate number of trained staff
