Epidemiology and Clinical Characteristics of Parainfluenza Virus Type 4 in Korean Children, 2015-2017

Background: Human parainfluenza viruses (HPIVs) are one of common causes of respiratory tract infections in children. Among the four serotypes (HPIVs 1-4), little is known about the epidemiology and clinical characteristics of HPIV-4. The aim of this study is to identify the epidemiology and the characteristics of HPIV-4 compared to HPIVs 1-3 in Korean children.

Methods: We reviewed medical records of children with HPIV who had been admitted at Seoul National University Children’s Hospital during 2015-2017. Detection of respiratory viruses in nasopharyngeal aspirates was performed using multiplex reverse transcription polymerase chain reaction. Patients who had underlying medical conditions such as chronic respiratory disease, immunodeficiency, congenital heart disease or concurrent viral infections were excluded.

Results: Of 12,539 samples, 586 (8.1%) were positive for HPIV. By the exclusion criteria, 137 (23.4%) were finally included: 46 (33.6%) for HPIV-3, 34 (24.8%) for HPIV-1 and -4 respectively, 23 (16.8%) for HPIV-2. During the study period, two seasonal outbreaks were observed in each serotype. HPIV-1 was prevalent in September 2015 and August 2016, while HPIV-2 in August 2015 and July 2017. The peak of HPIV-3 infection occurred in July 2016 and May 2017. HPIV-4 was mostly infected from August to September in 2015 and in June 2017. Regardless of serotypes, HPIV was predominantly observed in boys and among children less than 5 years of age (70%); the median age in HPIV-4 was 3.1 (0-18) years. The most common clinical presentation was cough in all serotypes (78.7-88.2%). Sore throat was mainly presented in HPIV-4 infected patients compared to other serotypes (11.8%; P=0.029). HPIV-4 infection was more often diagnosed as bronchiolitis (32.4%) compared to HPIV-1 (8.8%; P=0.016) and -2 (8.7%; P=0.037). Croup was most frequently diagnosed in children with HPIV-2 (21.7%), but no patients with HPIV-4 had croup (P=0.008).

Conclusion: We observed seasonal peak in HPIV-4 from late spring to autumn. Lower respiratory tract infection was main clinical manifestation in HPIV-4 among hospitalized patients and HPIV-4 is a common respiratory pathogen causing significant morbidity in Korean children during 2015-2017.