From the Guidelines
Parainfluenza viruses are the most common cause of croup, accounting for approximately 75-80% of all croup cases in children. The provided evidence does not directly answer the question of how often parainfluenza causes croup, but based on general medical knowledge and previous studies, it is known that parainfluenza viruses are the leading cause of croup in children. Specifically, parainfluenza virus types 1 and 2 are responsible for the majority of these cases, with type 1 causing outbreaks in the fall every two years and type 2 causing annual outbreaks 1.
Key Points
- Parainfluenza virus type 3 more commonly causes bronchiolitis and pneumonia but can also lead to croup.
- The virus typically infects the upper airway, causing inflammation and narrowing of the subglottic region, which results in the characteristic barking cough, stridor, and respiratory distress associated with croup.
- Children between 6 months and 3 years of age are most susceptible to developing croup from parainfluenza infection due to their smaller airway diameter.
- Treatment typically involves corticosteroids such as dexamethasone (0.6 mg/kg, maximum 10 mg) as a single oral dose to reduce inflammation, and in more severe cases, nebulized epinephrine (racemic epinephrine 2.25% solution, 0.5 mL in 2.5 mL normal saline) may be administered to temporarily reduce airway swelling.
It's worth noting that the clinical course of croup caused by influenza appears to be more severe than croup caused by the more common parainfluenza virus, and is more likely to be complicated by bacterial tracheitis 1. However, this information does not change the fact that parainfluenza viruses are the most common cause of croup in children.
From the Research
Croup and Parainfluenza
- Croup is a common illness that affects about 3% of children a year, usually between the ages of 6 months and 3 years 2, 3.
- The majority of croup infections, approximately 75%, are caused by the Parainfluenza virus 2.
- Parainfluenza virus types 1 to 3 are the most common causes of croup 4.
Symptoms and Treatment
- Symptoms of croup usually resolve within 48 hours, but severe infection can lead to pneumonia, respiratory failure, and arrest 2.
- Treatment for croup includes corticosteroids, such as dexamethasone, and nebulized epinephrine for moderate to severe cases 4, 3, 5.
- Humidification therapy has not been proven beneficial in treating croup 4, 5.
Management and Hospitalization
- Most episodes of croup are mild, with only 1 to 8% of patients requiring hospital admission, and less than 3% of admitted patients requiring intubation 4.
- A single dose of dexamethasone is recommended for all patients with croup, including those with mild disease 4, 3.
- Nebulized epinephrine is an accepted treatment for patients with moderate to severe croup, and multidose nebulized epinephrine may have a role in outpatient management 6.