I'm dealing with croup right now too. I read it is 1) viral (starts with a cold and progresses) or 2) allergies (like pollen and such). But it also has to do with little vocal cords/trachea/wind pipe. When catching a cold or allergy reaction, the wind pipe gets swollen and then you get the cough. You don't' get it in bigger kids b/c their windpipe has grown and when swollen it doesn't effect it the same way in a little one.
My advice nurse also said it could have to do with the weather. Out here in my area of CA we have has super cold and foggy weather one week, then gloriously sunny and warm, then back to cold, then warm again. She said the croup cases are up right now and believes the weather pattern has something to do with it. Maybe its been like that in Davenport??
Good luck! I'm right there with you!