Mapping Covid in NZ: Genome says?

Things I learned from what looks to be a superb study on Covid in New Zealand using genetic analysis of 56% of all confirmed cases:

1. Only 19% of cases that came into New Zealand resulted in more than one additional person being infected while 24% led to a single additional infection - presumably policy substantially reduced transmission;
2. Lockdown reduced R-naught of our biggest cluster from 7 to 0.2 within a week;
3. The 649 cases analysed showed 277 separate introductions of the virus into New Zealand;
4. There is no evidence of the virus circulating before the first reported case on 26 February;
5. The largest cluster came from the US, and North America provided most of the cases resulting in transmission linkages.

I was very worried in February that it had already gotten here. Somehow, it hadn't. We've been very lucky. 

Oh, and obviously, lockdown worked.