Croup is a respiratory illness in children that may be caused by multiple viruses including RSV, influenza, adenovirus, rhinovirus, and parainfluenza.  Parainfluenza is the most common cause of croup which is characterized by a barking cough in young children and hoarseness in older kids.  Croup commonly occurs in outbreaks at different times of the year, however parainfluenza is more common in the fall and winter months.  Like other respiratory illnesses, croup is spread by way of respiratory droplets in the air or on contaminated objects such as hands and doorknobs.  There is no specific treatment for the croup (unless it is caused by influenza) although medicines may help lessen the symptoms.  Symptoms usually resolve without treatment within 1 week.

Asthma (sometimes called reactive airway disease in younger children) is a chronic respiratory illness that affects millions of children worldwide.  It is characterized by airway inflammation and narrowing that leads to cough, wheezing, excercise intolerance, breathing difficulty and even respiratory distress. 

The influenza virus causes "the flu," which is an illness with a variety of symptoms such as high fever, malaise (generally feeling sick), chills, headache, cough, and muscle aches.  The fever and muscle aches are common in influenza and help with the diagnosis.  A rapid test is available for use in clinics and hospitals.  If the diagnosis is made within the first 48 hours of symptoms, an antiviral medicine can be given that will shorten the course of the illness.  Otherwise treatment is based on lessing the symptoms.  The majority of the symptoms typically resolve within 1 week.  The influenza vaccine is effective in preventing the flu, although not all strains of the virus are covered by the vaccine.