A second case of measles has been confirmed and health experts warn it has the potential to "spread like wildfire" if people aren't immunised.
The cases are linked, which Te Whatu Ora says is reassuring, but it could be several days before we know if there are further infections.
If there's one thing that sets measles apart from other illnesses, Professor Nikki Turner from the Immunisation Advisory Centre put it bluntly.
"It can spread like wildfire through a community," she told Newshub.
And that's why Albany Senior High School started online learning on Friday as investigations into the first infection - a student at the school - continue.
The second confirmed case is a household contact of the first student. They recently travelled overseas, providing a link to the border, and it was to a country known to have measles.
"We are confident this person is the source of this infection," said Dr William Rainger from Te Whatu Ora.
In an update on Friday, Te Whatu Ora said no new cases have been confirmed as contact tracing continues.
"Auckland Regional Public Health Service is continuing to work closely to support the school and the community. We are working as quickly as possible to test staff who may not be immune and to complete contact tracing for students and staff, with a focus on supporting the school to reopen safely as soon as is possible," it said in a statement.
"A pop-up testing centre was set-up in Massey this morning to carry out testing of staff who do not have records of immunity. These samples are being prioritised for processing by laboratories, to speed up public health immunity checks and ensure staff can be cleared to leave quarantine if it is safe to do so."
Early investigations have revealed that almost 80 percent of students have either had one or two doses of the MMR vaccine.
Staff immunity is still being worked through, and that will be the key decider of whether Albany Senior High reopens on Monday.
Dr Rainger added: "If a person has not had two doses of MMR, then we are asking for them to remain in quarantine."
Chemist Warehouse in Albany is a location of interest - but from way back on April 20.
Measles can take up to 10 days to develop, and then potentially a further four days to show symptoms.
"So we can't let our guard down at this stage," said Dr Rainger.
On top of that, Prof Turner said measles symptoms can be easily mistaken for something else.
"At the start it looks a bit like a cold, with a cough [and] a runny nose. It's a really chesty cough. You get red eyes, and then after over two-four days you get the rash."
Tend Health co-founder Dr Mataroria Lyndon said tamariki are some of the most vulnerable.
"Especially the under-five-year-olds. They're at risk of complications from measles in terms of hospitalisation."
And one doesn't have to look far to understand how deadly it can be.
In 2019, about 6000 people came down with measles in Sāmoa. Eighty-three people died, and the majority were young children.
"It's not a disease I would wish on anyone," said Prof Turner.
But it could all be avoided, with one crucial tool, according to Dr Lyndon.
"It is vaccine preventable," he said.
In other words - measles is preventable