Season One Edit. Beckett's initial relationship with Castle was strained because she viewed him as immature and reckless. She suspected (correctly) that Castle was using his research as an excuse to pursue her, and only tolerated his presence at the request of Captain Montgomery.
What causes croup in children. Croup in children is most often caused by the parainfluenza virus, a respiratory virus not related to the flu. But it can also be caused by other respiratory viruses including the flu. Yes, croup is contagious.
However, older children up to 15 years old sometimes get croup too. Croup is a common respiratory condition in children caused by either a viral infection or allergy. It affects the windpipe, larynx (voice box) and airways to the lungs, which can become inflamed or filled with mucus.