evidence: New Zealand's COVID-19 cluster was linked to the Sydney outbreak. But mystery surrounds how it got into the community [...] It had been a key plank in New Zealand's coronavirus strategy, keeping the island COVID-19-free for a majority of the pandemic and heralded as one of the world's best at containing the virus. [...] This phenomenon is called "overdispersion," and has been a common feature of COVID-19 outbreaks in New Zealand and elsewhere, Dr Kvalsvig said.