BACKGROUND: Human parainfluenza viruses (HPIVs) were first discovered in the late 1950s, and recognized worldwide as
the leading cause of acute respiratory infections (ARIs) for children under the age of five. These viruses are antigenically and
genetically classified into Types 1 to 4. The clinical features are associated with both upper respiratory tract infections
(URTIs) and lower respiratory tract infections (LRTIs). HPIVs are generally transmitted from an infected person to others
through the air by coughing, sneezing and close personal contact. Although HPIVs are recognized as one of the causative
agents for ARIs, there is no vaccine to prevent these and specific antiviral treatment for HPIV infection is not yet available.

SUMMARY: During the nationwide study conducted from September 2015 to August 2016, 777 samples tested positive for
HPIVs. These viruses were prevalent among children under the age of five and the frequency of detection rate in Type PIV1,
2 and 3 was 37.58% (292), 11.84% (92) and 50.58% (393), respectively. Also, different prevalence patterns were identified
and seasonality depended on the subtypes: PIV-1 circulated from summer to autumn, while PIV-3 was prevalent during
summer. However, HPIV-2 and HPIV-4 did not have an annual seasonal pattern. In addition, age and seasonality
characteristics were similar to other countries such as Japan, China and USA. In conclusion, the distribution of viruses
according to age and season is useful to predict trends of viruses and may help prevent their occurrence.