Has anyones dog ever had flu like syptoms?

i have never experienced it or heard of it before!! my youngest dog started first with a congested breathing... I thought it was maybe an allergy or he had something lodged, so i flushed his nasal pages and he sneezed a lot of green, thick mucous. As it started to clear (after about 5 days) my other 2 dogs developed the same symptoms, so it was obviously transmittable!! has Anyones dog ever experienced this?? as i always belived dogs didnt get colds and flu ????