H parainfluenza viruses (HPIVs) have been recognized as a cause of respiratory tract infections for many decades. They belong to the Paramyxoviridae family, subfamily Paramyxovirinae, and are classified into 4 serotypes. Serotype 4 can be further subdivided into 2 antigenic subtypes, HPIV-4A and HPIV-4B (1). Although the epidemiology and clinical manifestations of serotypes HPIV-1 to HPIV-3 are...