0. Obviously it is not ideal that border/MIQ workers were not being tested. But is this failure to blame for the current outbreak? Some thoughts on the "border worker hypothesis...(might be wrong)...

1. As of last reporting no border workers have tested positive. If that testing continues to be all negative then that would be evidence against the border worker hypothesis

2. Border workers are health checked daily. So any infection of a border worker (B) would be an asymptomatic border worker infection.

3. 1 and 2 combine to make a very low probability event.

4. Onward transmission would be relatively low probability from B as they would have been asymptomatic. While asymptomatic transmission can occur it happens much less frequently than pre/symptomatic transmission

5. If a border worker were the infection source then they must have got it from a traveller (T) and be a link in the chain between the traveller and current outbreak index case (I).That is, T > B > ... I. Genomic data suggests no such chain exists (genomic data all done?).

6. For an unidentified traveller case to infect the border worker that traveller must have had 2 negative tests and have been asymptomatic. This is very low probability.

7. Contact tracing has revealed no backward link between index case and border (B > I). If an asymptomatic T infected an asymptomatic B then they must have asymptomatically infected at least one other person (Missing - M). So the chain would need to be T > B > M > I at minimum.

8. Contact tracing and testing have not revealed any such case (M). It is probably more likely that that person M would be asymptomatic also - else if they were symptomatic they would have been more likely to be identified.

9. Since MIQ starting there have been no reports of any previous infection control failures resulting in a symptomatic border worker. Nor has there yet been reported an asymptomatic border worker setting of a transmission chain. That is, ifa failure thenmost-likely the first.

10. So where does this leave us? We need to wait until the border testing (to identify B) and genomic data analyses are complete (which would establish T >.... I) . If they all turn up negative then all-in-all the border worker hypothesis is an extremely low probability event.

11. Oh also currently no cases have been found upstream from I. This would imply a single transmission chain from B>M>I. But given level 1 settings & R0 2-5 this lack of branching is low probabilty.

12. Oddly M would know what is going on and that MoH are looking for a connection person B>M. One would think M would know they are this person. Of course there could be an N ...