Seasonality and etiology of croup in pediatric patients hospitalized with lower respiratory tract infections: A long-term study between 2009 and 2017

Kyung Jin Oh; Dong Hwa Yang; Hyeong Rok Shin; Eun Jin Kim; Yong Han Sun; Eell Ryoo; Hye Kyung Cho; Hye Jung Cho

doi:10.4168/aard.2019.7.1.28

Journal List > Allergy Asthma Respir Dis > v.7(1) > 1125515

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Oh, Yang, Shin, Kim, Sun, Ryoo, Cho, and Cho: Seasonality and etiology of croup in pediatric patients hospitalized with lower respiratory tract infections: A long-term study between 2009 and 2017

Original Article

Allergy Asthma Respir Dis 2019;7(1):28-36.

Published online: 12 January 2019

DOI: https://doi.org/10.4168/aard.2019.7.1.28

Seasonality and etiology of croup in pediatric patients hospitalized with lower respiratory tract infections: A long-term study between 2009 and 2017

Kyung Jin Oh, Dong Hwa Yang, Hyeong Rok Shin, Eun Jin Kim, Yong Han Sun, Eell Ryoo, Hye Kyung Cho, Hye Jung Cho

^¹Department of Pediatrics, Gachon University Gil Medical Center, Gachon University College of Medicine, Incheon, Korea

Correspondence to: Yong Han Sun https://orcid.org/0000-0003-1527-6782 Department of Pediatrics, Gachon University Gil Medical Center, Gachon University College of Medicine, 21 Namdong-daero 774beon-gil, Namdong-gu, Incheon 21565, Korea Tel: +82-32-460-3224, Fax: +82-32-460-2362, E-mail: chdsyh@gilhospital.com

Received 5 September 2018 Revised 16 October 2018 Accepted 16 October 2018

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

Croup is a common respiratory disease in children. The aim of this study was to analyze the epidemiology, etiology, and seasonal variations of respiratory virus infections in children with croup.

Methods

From October 2009 to September 2017, children admitted with croup to Gachon University Gil Medical Center under the age of 18 years were enrolled in this study. We retrospectively reviewed patients’ medical records.

Results

A total of 1,053 of 27,330 patients (3.9%) infected with lower respiratory infections were diagnosed as having croup. In the age distribution, croup was most common (50.0%) in children aged 1 to <2 years. There were 2 peaks, the major in summer (July to August) and the minor in spring (March to May). Parainfluenza virus type 1 (15.8%) was most prevalent and coincided with the summer peaks of croup. Influenza virus type B and parainfluenza virus type 3 were the most frequent etiologic agents in a spring peak of croup. Although parainfluenza virus type 1 was predominant of all ages, human coronavirus was a significant cause of croup in children younger than 1 year, whereas influenza virus played an important role in children above the age of 3 years.

Conclusion

Seasonality and epidemiology of croup varied with age and regions. Two peaks of seasonal fluctuation were in summer and spring, which were related to the seasonality of respiratory viruses in croup. These results may be helpful in planning clinical and research needs.

Keywords: Croup, Epidemiology, Seasonality

References

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Fig. 1.

Frequency of lower respiratory infections and croup by age group. Values are presented as number. LRI, lower respiratory infection.

Fig. 2.

The number of viral agents in croup patients including mixed infections and simple infections. Percentage is the ratio of each virus that is mixed cases. PIV, parainfluenza virus; RSV, respiratory syncytial virus; ADV, adenovirus; IFV, influenza virus; HcoV, human coronavirus; hMPV, human metapneumovirus; HRV, human rhinovirus; HBoV, human bocavirus.

Fig. 3.

Monthly incidence of total croup and monthly incidence of croup according to 5 respiratory viruses from 2009 to 2017. PIV, parainfluenza virus; IFV, influenza virus; hMPV, human metapneumovirus.

Fig. 4.

Monthly incidence of viruses detected in patients with croup from 2009 to 2017. PIV type 1,2,3,4 (A), IFV A, B and RSV A, B (B), HcoV, hMPV and HRV (C), HBoV, ADV and HEV (D). PIV, parainfluenza virus; IFV, influenza virus; RSV, respiratory syncytial virus; HcoV, human coronavirus; hMPV, human metapneumovirus; HRV, human rhinovirus; HBoV, human bocavirus; ADV, adenovirus; HEV, human enterovirus.

Fig. 5.

The number of cases hospitalized with croup and detected respiratory viruses per month for 8 years. The dotted arrows indicate the peaks of croup (more than 15 cases), and the solid arrows indicate viruses that affected peaks of croup. PIV, parainfluenza virus; RSV, respiratory syncytial virus; IFV, influenza virus; HcoV, human coronavirus; HRV, human rhinovirus; HBoV, human bocavirus; hMPV, human metapneumovirus.

Table 1.

Distribution and incidence by sex according to patient age in patients with croup

Age	Male, n (%)	Female, n (%)	Incidence by sex (M/F)	No. of cases (%)
<1 yr	118 (11.2)	106 (10.1)	1.1	224 (21.3)
0–6 mo	20 (1.9)	11 (1.0)	1.8	31 (2.9)
6–12 mo	98 (9.3)	95 (9.0)	1.0	193 (18.3)
1–2 yr	325 (30.9)	201 (19.1)	1.6	526 (50.0)
2–3 yr	128 (12.2)	60 (5.7)	2.1	188 (17.9)
3–4 yr	37 (3.5)	15 (1.4)	2.5	52 (4.9)
4–5 yr	18 (1.7)	14 (1.3)	1.3	32 (3.0)
5–7 yr	16 (1.5)	5 (0.5)	3.2	21 (2.0)
≥7 yr	6 (0.6)	4 (0.4)	1.5	10 (0.9)
Total	648 (61.5)	405 (38.5)	1.6	1,053 (100)

Table 2.

Etiologic agents isolated from patients hospitalized with croup

Virus identified	No. of cases (%)
Parainfluenza virus type
1	104 (15.8)
2	27 (4.1)
3	31 (4.7)
4	2 (0.3)
Influenza virus
A	37 (5.6)
B	34 (5.2)
Respiratory syncytial virus
A	47 (7.2)
B	21 (3.2)
Human rhinovirus	58 (8.8)
Human coronavirus	52 (7.9)
Human metapneumovirus	24 (3.7)
Adenovirus	15 (2.3)
Human bocavirus	13 (2.0)
Human enterovirus	1 (0.2)
Mixed	191 (29.1)
Total	657 (100)

Table 3.

Age distribution and mean age of children hospitalized with croup for each virus

Age (yr)	PIV			RSV A	RSV B	ADV	IFV A	IFV B	HcoV	hMPV	HRV	HBoV C	Cases of croup with isolated
Age (yr)	Type 1	Type 2	Type 3	RSV A	RSV B	ADV	IFV A	IFV B	HcoV	hMPV	HRV	HBoV C	Cases of croup with isolated
0–1	14 (10.6)	10 (7.6)	5 (3.8)	9 (6.8)	2 (1.5)	2 (1.5)	5 (3.8)	5 (3.8)	19 (14.4)	3 (2.3)	16 (12.1)	3 (2.3)	132
1–2	63 (18.2)	8 (2.3)	19 (5.5)	28 (8.1)	15 (4.3)	11 (3.2)	13 (3.8)	9 (2.6)	24 (6.9)	14 (4.0)	29 (8.4)	8 (2.3)	346
2–3	16 (14.3)	6 (5.4)	5 (4.5)	8 (7.1)	4 (3.6)	2 (1.8)	6 (5.4)	7 (6.3)	6 (5.4)	4 (3.6)	6 (5.4)	2 (1.8)	112
3–4	6 (20.0)	1 (3.3)	2 (6.7)	0 (0)	0 (0)	0 (0)	6 (20.0)	2 (6.7)	2 (6.7)	2 (6.7)	1 (3.3)	0 (0)	30
4–5	4 (26.7)	0 (0)	0 (0)	1 (6.7)	0 (0)	0 (0)	1 (6.7)	4 (26.7)	0 (0)	0 (0)	5 (33.3)	0 (0)	15
5–7	1 (6.7)	2 (13.3)	0 (0)	1 (6.7)	0 (0)	0 (0)	6 (40.0)	2 (13.3)	1 (6.7)	0 (0)	0 (0)	0 (0)	15
≥7	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	5 (71.4)	0 (0)	1 (14.3)	1 (14.3)	0 (0)	7
All ages	104 (15.8)	27 (4.1)	31 (4.7)	47 (7.2)	21 (3.2)	15 (2.3)	37 (5.6)	34 (5.2)	52 (7.9)	24 (3.7)	58 (8.8)	13 (2.0)	657
Age (mo	) 21.0±11.7	20.5±16.1	19.2±8.7	19.8±11.1	17.3±5.5	17.9±4.6	30.6±21.1	39.2±29.8	16.9±11.6	22.4±15.6	20.8±17.2	16.4±6.0

Values are presented as number (%) or mean±standard deviation. The denominator is the number of cases with isolated virus for each age group.

PIV, parainfluenza virus; RSV, respiratory syncytial virus; ADV, adenovirus; IFV, influenza virus; HcoV, human coronavirus; hMPV, human metapneumovirus; HRV, human rhinovirus; HBoV, human bocavirus.

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