Viral causes of croup are considered contagious and transmitted through airborne droplets of infected respiratory fluids (and mucus). A child or adult may inhale these droplets via a cough or a sneeze from an infected individual or through direct contact (touch) with an infected individual.
Viral particles may also live on objects such as table tops, furniture, doors and other surfaces, or toys, which when touched can be transferred during direct contact with the eyes, nose or mouth (indirect contact) thereafter.
Adults looking after children with croup or those in close proximity to infected children can also be infected with the viruses that cause the illness. When infected, adults generally don’t experience the stridor or breathing difficulties associated with croup, but instead suffer from laryngitis (inflammation of the voice box that causes a loss of voice).