I watched a TV program last week which blamed the Spanish Flu on the US Army.
Specifically the Flu started in the mid-West and spread around the soldiers who were training. Ignoring the complaints from some, the soldiers were packed into ships and sent to Europe where something like 2/3rds of them were unable to perform.
In Spain there were no reporting restrictions and the malaise was widely reported. Everywhere else there was a war going on and reporting was tightly controlled.