Most common cause of Bronchiolitis is ?

<a href=" syncytial virus (RSV)</a> is the most common cause of bronchiolitis. Sometimes, the common also can cause it. Bronchiolitis is one of the common serious acute lower respiratory tract infection in infants. Affected infants are between ages of 1 and 6 months but the disease can affect children upto 2 years old.Disease usually occur in winter and spring .Respiratory syncytial virus is implicated in most cases.other causative agents include parainfluenza virus,influenza virus,adeno virus,Mycoplasma. protection against RSV is mediated by antibodies of IgG3 subclass. Ref : ESSENTIAL PEDIATRICS,O.P.GHAI,PG NO:356,7th edition