Thread by @AbraarKaran

1/ #covid19 outbreak investigation of the Yokohama Cruise Ship

Over 3 week period, 20% of passengers infected; 14% of staff

Attack rate was highest in cabins of size 4 or more-- 30%

Not convinced by their thoughts on mode of transmission..
wwwnc.cdc.gov/eid/article/26…

2/ They mention that there didn't seem to be spatial clustering of infected cabins on the same floor/zone, & that this implies it was not primarily spread via droplets/ more evidence it was potentially spread by aerosolized particles?

This doesn't make sense to me.

3/ Most people prob aren't interacting closely w/ other random cabins on their floor but do share same hallways at diff times.

If anything, clustering by floor/zone in which people don't interact face to face as much would suggest lingering aerosols- which we didn't see here.

3.5/ I think it is hard to conclude mode of transmission here one way or the other, & personally still fall in the camp that transmission happens via particles of many sizes.

Interested in other people's thoughts on this.

cc @zeynep @RanuDhillon @PaulSaxMD @BhadeliaMD

4/ Many of us have said this but worth repeating: cruise ships are high risk by design; we have seen many outbreaks of #covid19 on these.

I would avoid them.

Rmr that symptom & temperature checks are not good enough to catch all cases-- transmission starts pre-Sx

5/ Even rtPCR testing pre-entry is not fool proof, as tests are snapshots in time.

Could be negative the day of your test; could be infected & infectious a couple of days after, without symptoms.

Needs a thoughtful strategy (there are some) but would avoid cruising for now.

Cc @V2019N @InfectiousDz