A deep-clean has been undertaken at an Auckland KFC after a community case of COVID-19 went to work instead of isolating.

The employee, referred to as Case L, was at work at the Botany Downs' KFC on Monday afternoon through to Tuesday after midnight. 

Otago University Professor of Public Health Michael Baker says compliance is critical - and if people ignore the rules, Auckland could find itself back in lockdown.

"I think it's even more vital than usual that people in Auckland do act if they have any symptoms at all - because that's the thing that will make the difference between this being a controllable outbreak, and one that requires more drastic action," he told Newshub.

On Tuesday, it was revealed that another student at Papatoetoe High School had tested positive - Case I - who caught the virus from the original case at the school, Case A.

Later that day, two other people in Case I's household had tested positive and one of them - Case J - had been to work at Botany's Kmart.

The latest case - Case L - is the fourth in the household. They had been working at KFC Botany on Monday and Tuesday - the day other members of their household tested positive.

"Clearly this person, Case L, was negligent and broke the rules and may put a large cost onto many other people," ACT leader David Seymour told Newshub.

The Ministry of Health says it took several steps to try and inform the family about the need to self-isolate, but it couldn’t reach them. 

A spokesperson says they phoned "several times" on two different phone numbers and followed up with three text messages. The Auckland Regional Public Health System (ARPHS) also sent a letter to the family, as well as via email and Facebook. 

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Professor Baker says it would be worrying if Auckland begins to record cases that cannot be linked to the current cluster - however, it's "good news" that the existing infections are genomically linked.

He says that at this stage, the new cases are "not unexpected" - but the risk remains that the outbreak could become increasingly difficult to contain.

"The Government is now facing a rolling wall of cases. They're running through the alphabet so quickly, we're up to L and might run out of letters," Seymour said.

Case L went to work at 3:30pm on Monday and finished at 12:30am.

The 11 KFC staff on the same shift, classified as close-plus contacts, have been asked to get tested and self-isolate.

The customers who were in the store at the time are considered close contacts. They also need to self isolate and are asked to get tested twice.

Drive-thru customers are considered casual-plus contacts, and are also required to self-isolate until they return a negative test. 

It was clear on Friday that locals are unimpressed.

"It's not responsible and not fair to others," one woman told Newshub.

"Don't think about yourself. Think about everyone else around you," said another.

"They should be ashamed. Everyone's done such a hard job last year and everyone should be doing their part."

Prime Minister Jacinda Ardern says the public health advice has shifted up a gear, with more and more people being asked to isolate and get tested.  

"We're going further than we usually do, as that allows the rest of the country to stay at level 1," she said on Friday. 

Level 1 is where New Zealand wants to stay - and the coming days could be crucial to deciding if we'll remain there.