If you can say for certain that you haven't been any where where you may have been exposed and brought it home...then yes. If you've visited someone who has chickens that have or have had these symptoms in the past, you handled their birds, or birds anywhere else, it is possible it could have been introduced that way. Where they are 4 weeks now I wonder about the incubation period for these diseases, especially when they would be showing sign if it did pass through the egg from the parents. I don't know, I'm not that smart.