Causes and types of croup
What are parainfluenza viruses?
A group of four viruses known as human parainfluenza viruses (HPIVs) are responsible for causing different illnesses and their associated symptoms. All viruses in the group cause infections in either the upper or lower respiratory system.
Of the four known virus types, HPIV-1 and HPIV-2 can cause croup infections. HPIV-1 is the type which more commonly causes croup, with HPIV-2 occurring less often. HPIV-3 is more commonly seen in infections such as pneumonia and bronchiolitis. HPIV-4 is the rarest type of the four viruses and unlike the others, doesn’t appear to have seasonal patterns.
The most common types of croup are:
- Viral croup (Laryngotracheobronchitis): A parainfluenza virus infects the larynx and trachea and displays initial symptoms which are similar to that of the common cold, such as nasal congestion and a runny nose. A child will soon develop a barking cough, and make high-pitched (loud), and harsh wheezing noises (stridor) when breathing in (inhaling). A low-grade fever is also common with this viral infection.
- Spasmodic croup (spasmodic laryngitis): Infection typically comes on suddenly and can be quite distressing for both the child and their parents / caretakers. A child may awaken out of the blue, gasping for breath and also display signs of stridor, a barking cough, as well as a hoarse voice. General symptoms are just like that of viral croup but unlike the virally caused type, spasmodic croup does not typically present symptoms of fever (i.e. it does not have a contagious cause which would cause a fever). Spasmodic croup is believed to be linked more closely with acid reflux (where the contents of the stomach travel back up the oesophagus) or an allergic reaction.