Case 2

1. How is the virus transmitted? 

Transmission is via direct inhalation of particles or contact with contaminated secretions to nasal or conjunctival epithelium. Parainfluenza is a disease seen primarily in children 4 months to 6 years of age. Epidemic disease occurs in the fall with PIV-1 or PIV-2 predominantly in alternate years. PIV-3 appears to be endemic throughout the year. Like all enveloped respiratory viruses, PIV is spread most efficiently by aerosolization.

2. What is croup? Why don’t adults get croup? 

The pathophysiology of croup is due to infection and inflammation in the subglottic area. This leads to a stridorous cough. Manifestations of parainfluenza virus infections are generally more severe in infants and young children than in adults. (adult have a larger subglottic area and therefore the inflammation does not lead to as severe a cough). Infection can result in severe pneumonia, bronchitis, laryngitis, croup (laryngotracheobronchitis), or just a mild upper respiratory tract infection. There are no extrapulmonary manifestations (no viremia).

3. Describe how the clinical diagnosis of croup was confirmed. Is laboratory confirmation critical in all cases? 

Laboratory confirmation is not critical in cases with "classic" clinical presentation.


There is attached a copy of the procedure for working up respiratory specimens.

4. Is this child likely to be re-infected? What is the common symptom in adults with this infections? 

Yes. Immunity is only transient. Repeat infections, which are usually milder, occur in older children and adults.

5. If this child had more severe croup, what treatment would be appropriate? 

Recent studies indicate that in children with moderately severe croup, treatment with intramuscular dexamethasone or nebulized budesonide resulted in more rapid clinical improvement than did the administration of placebo, with dexamethasone offering the greatest improvement. Treatment with either glucocorticoid resulted in fewer hospitalization.