My son had it and was pretty much asymptomatic.
Albuterol Sulfate (asemia spray) or Levalbuterol in a nebulizer will help in breathing if his branchial tubes are inflamed or gets Bronchitis. I completely agree with the vitamins recommended as well, just make sure he takes them with food and not on an empty stomach.
My son had it and was asymptomatic except for a cough.