i haven't had the flu since... ummmm 1993. that's 13 years. i still remember it, it was the fall i returned to graduate school. i wash my hands a lot in the winter, avoid big crowds of people, overheated places, eat well, get plenty of rest and exercise, and keep my house on the cool side. i drink 2000 mg of vitamin C each day and take fish oil and viamin D. when i'm not pregnant i sometimes take astragalus every day in the winter. i think that does a lot to boost my immune system. (pregnant women have super charged immune systems anyway)
i use zinc, oscillo, garlic and olive leaf extract when i get sick.
as far as oregeno oil goes, i have never ever heard it did anything for a virus or to boost the immune system. i know that it can be used to treat bacterial and fungal infections. and it's considered "the big guns." something to use when nothing else has helped. i would not consider it a preventative herb. and since cold and flu are caused by viruses, it doesn't seem like it would do much for flu season.
here's short article i found that was in "natural health" magazine:http://www.findarticles.com/p/articl...32/ai_91563260