There are four main human serotypes of hPIV: hPIV-1, hPIV-2, hPIV-3, and hPIV-4. hPIV-1 and hPIV-2 are most often associated with laryngotracheitis/croup in children. hPIV-3 is most often associated with bronchiolitis, bronchitis, and pneumonia. hPIV-4 may cause mild to severe respiratory tract infections.

Common symptoms include fever, runny nose, and cough but may also present with croup, which typically presents with a barking cough, hoarsness and stridor; bronchitis; bronchiolitis and pneumonia. Patients may occasionally experience sore throats, sneezing, ear pain, decreased appetite and rarely extrapulmonary manifestations may occur.

hPIVs spread via direct contact with infectious respiratory droplets or by airborne spread. The incubation period is generally 2-7 days.