When the school year has begun and the weather starts flip-flopping from cold to warm, we see a big increase in the number of cases of croup. This is a viral illness caused by parainfluenza virus. It is transmitted from one person to another the way other respiratory viruses are transmitted: being near someone who has coughed, spread their cough or nasal germs on to some surface someone else touches, etc.
Although it is the cough that sounds like a barking seal that tells us it is croup, what worries us about the illness is when the breathing is difficult (noisy, tight, or wheezy) in between the coughs when the child is breathing. See our protocol here for more information. Many of the hoarse voice (laryngitis), sore/scratchy throat, barky cough illnesses in the community are this illness.