Te Whatu Ora Southern Medical Officer of Health Dr Susan Jack said there were now 45 confirmed cases - up from 40 yesterday - 17 probable cases, and three under investigation.
"A source of infection has yet to be identified, but investigations are actively ongoing as we work to determine the source," Dr Jack said.
She said health officials were aware of some cases of secondary infection. "This means that there are some people who are getting it from people they live or work with."
Dr Susan Jack told RNZ last night the source could include drinking water, recreational water, food or drinks.
"We're still actively searching for the source ... so far nothing has come up as a red flag from our interviews with cases."
Because there was now person-to-person spread, she advised people to practise good hygiene.
"So handwashing with soap and water is absolutely critically, and especially drying your hands before you continue.
'Unfortunately, alcohol sanitisers are not effective for crypto, and then our other big message is not to go swimming until you've had no symptoms for at least two weeks."
