The difference being that it would take weeks to get to, say, Oz instead of hours. Anyone carrying the virus would have died on board ship before arriving...?
No, that’s not how it worked. The US troops who arrived In Europe by ship from the USA killed an order of magnitude more with the Spanish flu they brought with them than they did in combat.
What is sadly lacking from that period are accurate records of how many died from the flu over its three outings.