Paris ... if you add together all the food in all the supermarkets, corner stores, bakeries, butchers, pantries, basements and vending machines, Paris has a reserve of 48 hours.
If something were to interrupt the distribution of food, within two days, some two and a half million people will be without food. Though, of course, some have well stocked larders while other will be out of food by dinner time after whatever the event is.
That, right there, will be a massive breakdown in civilization. LA riots will seem like a barroom brawl.
An EMP that fries every piece of electronics in all of Paris will do the trick. The EMP will fry the entire rail infrastructure. Any modern cars or trucks will also be lost. Except for a handful of specially shielded of landlines, there will be no more phone communication and no internet.
Now, this is France we're talking about. If it's just Paris that's hit, they'll just have the army and airforce deliver food ... oh, and drinking water. Emp = no more pumps = one day's worth of tap water.
But it'll be pandemonium for a while.
And that's just Paris ... imagine this happening to ... say ... New York.
Now ... the superflu scenario ... A good number of people will abandon their jobs pretty much from day one. Hell, US-ians have skipped work because of ebola! Quite a few sectors can handle 10 ... 20 ... maybe 30% of employees skipping work. But the energy sector is especially vulnerable. Nuke plants can keep going with very few people operating them but coal plants are notorious in this regard. Even if power can still be generated, it still needs to get to the people. The power grid needs to be kept at 50Hz. Tiny fluctuations are ok, but a big deviation will destroy nearly every engine hooked up to the grid. Keeping the grid at 50Hz is a job that has so far not been automated successfully and only a handful of people know how to do this. Oh, and it takes about a year to learn it properly. So, if a just a couple of people bail, or you know, get the superflu and die, and there will be no more electricity.
Ever seen the TV series Revolution ... ?