Could RSV turn into croup. My 4month old has RSV he has had a cough 4 a while but now it sounds like a bark it gets better after breathing treatments?

Yes. RSV is a viral infection which may recur. It can cause croup, which affects the upper airway. The cough may be due to mucus plugs, constriction and inflammation of small airways in the lung. This infection is called bronchiolitis. Approximately 25% of children with RSV will respond to albuterol. Many of those children have a family history of asthma, or a history of a prior wheezing episode.
Yes. Rsv can be one of th causes of croup. The nebulizer is beneficial. Homeopathic spongia can also help with that barky cough...As can a cough medicine called chestal (both of which you can find at the health food store).