First things first : this is not the movie that will save 21st Century French comedies. It's pretty bad.
The plot makes no sense whatsoever: you would believe there are ghosts in the subways of Paris or an alien invasion in London before believing anyone would be dumb enough to confuse our super french weak main character with an east European revolutionary leader fighter type.
Dany Boon also just overplays it. In this movie he embraces being a new Louis de Funes... but does it quite pull it off. Even if he did, don't do this kind of stuff in 2014 no?
What does work sometimes is the premise of the main character : this germ and virus phobia did get a few chuckles here and there throughout the movie. Enough and often enough for me to plow through the whole thing.
Voila, you can probably pass though.