Tink, I watched a documentary on the 1918 Spanish flu, and learned that Woodrow Wilson got a really bad case of the flu while he was in France, negotiating the Treaty of Versailles. Wilson had been holding out against Georges Clemenceau, who wanted the vindictive reparations.
But after he recovered from the Spanish flu, Wilson was never the same...that flu was known for its destructive mental changes, and Wilson, exhausted, suddenly began to concede to whatever Clemenceau suggested.
And it was the harshness of that treaty which set the groundwork for WWII, making it virtually inevitable...speculations that World War II might not have happened without that one case of the flu!