Coronavirus: Two COVID-19 clusters 'closed' - what does that mean?

The Ministry of Health "closed" two significant COVID-19 clusters on Saturday after no cases were linked to them in weeks.

Clusters are groups of cases linked together as those with the illness are connected to one location, but are not all part of the same household. New Zealand has 16 significant clusters, meaning those with 10 or more cases of COVID-19, the deadly respiratory illness caused by the SARS-CoV-2 virus. 

Many of some these clusters have become well-known over the last month either due to the number of cases they have, such as the Bluff wedding, which has the most with 98, or for being linked to multiple deaths, like the Rosewood Rest Home cluster. 

On Saturday, the Ministry of Health "closed" two clusters, the Wellington and Auckland groups which travelled to the United States. Both had 16 cases of COVID-19 linked to them.

A cluster is "closed" after no case is linked to it for 28 consecutive days. This reflects two cycles of the virus' incubation period and means "there is no longer transmission of the virus within or associated with the cluster".

On top of the two clusters closed on Saturday, the Ministry previously closed the Wellington wedding cluster on Anzac Day. This cluster had 13 cases and was linked to overseas exposure.

While these clusters may be closed, that doesn't mean all cases within them have recovered. The Auckland group still has two active cases, while one case linked to the Wellington wedding is yet to recover.

A case is considered recovered after it has been at least 10 days since their symptoms emerged and when they have been symptom-free for at least two days. 

New Zealand's clusters:

  • Bluff wedding: 98 cases, linked to overseas exposure
  • Marist College, Auckland: 94 cases, unknown origins
  • Matamata Bar: 76 cases, linked to overseas exposure
  • Rosewood Rest Home, Christchurch: 55 cases, unknown origins
  • Stag party, Auckland: 39 cases, unknown origins
  • World Hereford Conference, Queenstown: 38 cases, linked to overseas exposure
  • St Margaret's Rest Home, Auckland: 35 cases, unknown origin
  • Community, Auckland: 30 cases, unknown origin
  • Ruby Princess Cruise Ship, Hawke's Bay: 24 cases, linked to overseas exposure
  • George Manning retirement village, Christchurch: 20 cases, unknown origin
  • Wellington group which travelled to the United States: 16 cases, linked to overseas exposure, closed
  • Auckland group which travelled to the United States: 16 cases, linked to overseas exposure, closed
  • Waikato rest home: 15 cases, linked to overseas exposure
  • Auckland rest home: 13 cases, linked to overseas exposure
  • Wellington wedding: 13 cases, linked to overseas exposure, closed
  • Christchurch workplace: 10 cases, linked to overseas exposure.