I heard that this "Grippe" was similar to the flu in symptoms but was notoriously known for it's severe cramping that would keep individuals on bed rest. It was also known as "La Grippe" or 'Spanish Flu" infamous in 1918, in which it carried into the 40's.
As I recall, "Grippe" is German for flu. Also, there is a song in "Guys and Dolls" which mentions "la grippe - ha - la grippe! La post-nasal drip!"
Anyway, I bet I'm not the only one who calls anything minor a cold, but if the same symptoms make me really miserable, it must be a flu! So I can imagine 70 years ago in the middle of a war nobody cared about the distinction.