As it now happens, we now account for incursions of Covid-19 coronavirus as if reciting the alphabet.
Sunday night's new case - a worker at the Grand Millennium hotel - is the third case at the hotel in recent weeks, and is known as Case C. Case A was a cleaner who tested positive on March 21 and Case B is the security guard who tested positive last week.
ABC and here we are, ready for D. Where will the alphabet stop this time? Complicating the simple rote is the lack of a known link between A and B. How did we get from A to B? There may need to be an A.1, perhaps, should that case ever be identified.
The red-letter issue in the Millennium Hotel chain of cases, however, is the lack of vaccination and testing which was exposed. Despite working in a managed isolation and quarantine facility, neither Case B nor C had been vaccinated.
The first batch of 650,000 doses of the Pfizer vaccine landed at Auckland International Airport on board a Singapore Airlines flight on February 15 - two months ago.
Director general of health Dr Ashley Bloomfield said he understood Case C wanted to be vaccinated but this was held up due to being in isolation after being linked to Case B.
Bloomfield said there was no problem with vaccine supply and he felt confident about the vaccine roll-out. This does not explain why Case B still hadn't been vaccinated by March 21 when Case A received the positive result.
A growing list of "locations of interest" linked to the infections now includes a barber, mobile phone store, a bakery, a dairy and three bus journeys.
MIQ Brigadier Jim Bliss says his team will continue to review processes and no findings or major issues had come from an audit of the situation. He said 98 per cent of staff at the hotel had been vaccinated and he expected the remaining 2 per cent to be vaccinated by the end of the week.
Bloomfield points out many people at the frontline have been vaccinated - everyone has been invited to be vaccinated but not everyone has taken up that offer. He said he always anticipated some MIQ staff would be unwilling to be vaccinated but now they have until the end of the month.
He again says there has been a high uptake. "About 80 per cent of border workers have been vaccinated and we are working to ensure the rest are vaccinated by the end of the month.
"It's very difficult to pin down how many people haven't been vaccinated."
It seems unfathomable that frontline staff who still want their jobs haven't turned up for vaccination appointments. Surely they are aware that catching the virus jeopardises their jobs, their health, their lives, not to mention others?
Finally, Bloomfield has declared any frontline staff not vaccinated need to move into other roles.
Yes, they do. They need to be where they are not exposing themselves and the rest of the team of five million to the steadily morphing variants of Covid-19. That's as easy to understand as ABC.