From the Research
Croup is primarily caused by viral infections, with parainfluenza virus being the most common etiology. The most recent and highest quality study 1 supports this, indicating that parainfluenza virus (types 1 to 3) is the most common cause of croup. Other viruses that can cause croup include respiratory syncytial virus (RSV), influenza virus, and human metapneumovirus. While these viral pathogens account for the vast majority of croup cases, rare instances can be caused by bacteria such as Mycoplasma pneumoniae. Non-infectious causes are extremely uncommon but can include allergic reactions or inhalation injuries.
Key Points
- The viral nature of croup explains its typical seasonal pattern, with peaks in late autumn and early winter 1.
- Understanding the viral etiology is crucial for management, as it guides treatment towards supportive care rather than antibiotics in most cases 2.
- The inflammation caused by these viruses leads to the characteristic "barking" cough and stridor associated with croup, due to swelling of the subglottic region of the larynx 3.
- A single dose of dexamethasone is recommended in all patients with croup, including those with mild disease, to reduce the severity of symptoms and the need for hospitalization 1.