A staff member working at the event was confirmed to have Covid-19 after being in contact with someone who had travelled overseas.
Leena Singh, incident controller for the health response in Waikato, said Matamata residents with symptoms of Covid-19 should contact Healthline or their GP and visit a Community Based Assessment Centre (CBAC). They also needed to tell staff if they had attended the Redoubt Bar during the previous two weeks, or if they had close contact with anyone who had.
This also applied to any visitors to the town who had visited the bar on March 17 for the St Patrick's Day celebration and who were experiencing symptoms.
Meanwhile, an assessment centre would be operating at the Matamata Civic Centre at 11 Tainui St from 3pm today.
Prior to centre opening in Matamata, residents had been forced to travel to Te Aroha Silver Fern Event Centre to get tested for Covid-19. The Te Aroha station opened on Saturday.
Singh said it was important to know whether there has been spread beyond Matamata. The public health team was working through the connections of those affected to track positive cases and eliminate true community transfer.
The Herald understands officials had also discussed the best way to contain the spread and have even considered road-blocking the small town of 6000 but decided against it because everyone was already self-isolating.
"With the alert level 4 lockdown now in effect, residents of Matamata can be assured that they are already undertaking the safest possible practice by isolating and should continue to follow the national guidance. To ensure they limit any further transmission people should avoid travel, wash their hands and practice social distancing," Singh said.
"Please stay in your bubble as this is the most effective way to eliminate the virus."
A spokeswoman for Redoubt Bar and Eatery Matamata earlier told the Herald one of their staff members who had contracted the virus was "recovering well".
"We are just hoping for the absolute best result for our beautiful community. It's heartbreaking and scary on so many levels."
Matamata-Piako District mayor Ash Tanner said residents were "a little bit concerned", especially when the cases were going up.