All of a sudden, flies are swarming my appartment. Where are they coming from?

Question

Everyday, I kill/send them outside, until there are none left. Then, a few hours later there are one or two and if we leave the house for the day, (we close the patio doors) when we return, there are five or six big flies inside. Could there be a nest? Is there such a thing and if so, where should I be looking for it and what does it look like? We always close the screen doors and we never had this problem before, so what gives?

Answer 1

Flies do not nest, but they do lay eggs that are hatching. The solution is the fly swatter, fly spray or a thorough cleaning of every nook and cranny in your home. Any space you miss will result in more hatching.  If you only have 5-6 a day, you are lucky. The bad infestations are dozens a day. Remove all food sources for the flies. They will not lay eggs without a food source for their eggs.

Answer 2

Demonic posession or the decaying bodies inside your walls...