[Goose]

My guess is that it was transmitted asymptomatically long enough for the chain to be untraceable and reared its head.

BC

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Isn't it also possible that it was contracted by interaction with asymptomatic residents in NZ?  (And I get that it would have to involve multiple asymptomatic transmitters, but still).

Sure, it could happen, but keeping an asymptomatic chain going with no symptomatic cases that got tested and came up positive is a very, very low probability event. They have gone 100 days without a reported case, so that would be a chain at least 7 asymptomatic people long and NO symptomatic cases that got tested at all. It is very probable there are some people in NZ who are sick with COVID-19 that for their own reasons chose not to get tested. That keeps an undetected pocket of infection going. It could also be an asymptomatic person who entered the country "irregularly". That is to me a much more probable explanation.

It probably came from Australia two or three transmission cycles ago, not 100 days ago.

BC

Not a bad bet, but that is my "irregular" comment. There is a travel ban for Australian citizens. You need to get an exemption to travel overseas. Visitors to New Zealand are required to quarantine for 14 days on arrival, including from Oz.   That should catch asymptomatic cases as well, should it not?

[Goose]

My guess is that it was transmitted asymptomatically long enough for the chain to be untraceable and reared its head.

BC

---

Isn't it also possible that it was contracted by interaction with asymptomatic residents in NZ?  (And I get that it would have to involve multiple asymptomatic transmitters, but still).

Sure, it could happen, but keeping an asymptomatic chain going with no symptomatic cases that got tested and came up positive is a very, very low probability event. They have gone 100 days without a reported case, so that would be a chain at least 7 asymptomatic people long and NO symptomatic cases that got tested at all. It is very probable there are some people in NZ who are sick with COVID-19 that for their own reasons chose not to get tested. That keeps an undetected pocket of infection going. It could also be an asymptomatic person who entered the country "irregularly". That is to me a much more probable explanation.

It probably came from Australia two or three transmission cycles ago, not 100 days ago.

BC

Not a bad bet, but that is my "irregular" comment. There is a travel ban for Australian citizens. You need to get an exemption to travel overseas. Visitors to New Zealand are required to quarantine for 14 days on arrival, including from Oz.   That should catch asymptomatic cases as well, should it not?