Comparisons of Clinical Features among Influenza A (H1N1) and Seasonal Influenza A and B during 2009 to 2010 at a Single Institution

Tae-Gon Kang; Mi-Jin Kim; Byoung-Gwon Kim; Hye-Sung An; Hyun-Jin Yun; Eun-Jeong Choi; Jin-A Jung

doi:10.7581/pard.2011.21.4.269

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Kang, Kim, Kim, An, Yun, Choi, and Jung: Comparisons of Clinical Features among Influenza A (H1N1) and Seasonal Influenza A and B during 2009 to 2010 at a Single Institution

Abstract

Pediatr Allergy Respir Dis 2011;21(4):269-276.

Published online: 20 January 2011

DOI: https://doi.org/10.7581/pard.2011.21.4.269

Comparisons of Clinical Features among Influenza A (H1N1) and Seasonal Influenza A and B during 2009 to 2010 at a Single Institution

Tae-Gon Kang, MD¹, Mi-Jin Kim, MD¹, Byoung-Gwon Kim, MD², Hye-Sung An, MD³, Hyun-Jin Yun, MD⁴, Eun-Jeong Choi, MD^4,, Jin-A Jung, MD¹

¹Department of Pediatrics, Busan, Korea

²Preventive Medicine, Dong-A University College of Medicine, Busan, Korea

³Department of Pediatrics, Good Moonhwa Hospital, Busan, Korea

⁴Department of Pediatrics, Ilsin Christian Hospital, Busan, Korea

책임저자:정진아, 부산광역시 서구 동대신동 3가 1번지 동아대학교 의과대학 소아과학교실 Tel: 051)240-5617 Fax: 051)242-2765 E-mail: jina1477@dau.ac.kr

Received 6 October 2010 Revised 19 July 2011 Accepted 25 July 2011

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

This study was performed to compare the clinical features of pediatric patients who were diagnosed with influenza A (H1N1) or seasonal influenza A and B during 2009 and 2010 at a single institution.

Methods

Among children who visited the Dong-A University Hospital with fever (>37.8) and ℃ acute respiratory symptoms from September 2009 to February 2010, 1,004 children who were diagnosed with influenza A (H1N1) or seasonal influenza A and B by reverse transcription-polymerase chain reaction (RT-PCR) were enrolled. Monthly incidence, fever duration before diagnosis, symptoms (fever, cough, rhinorrhea, sore throat, headache, vomiting, abdominal pain, diarrhea, seizure, and dyspnea) and signs (rales, wheezing) were reviewed retrospectively in each group based on medical records.

Results

Influenza A (H1N1) was detected in 944 patients (94.0%), followed by seasonal influenza A in 42 (4.2%) and seasonal influenza B in 8 (1.8%). The positive rate of influenza infection was highest in November 2009 (n=557, 55.5%). Mean duration of fever before RT-PCR was 1.6 days (range, 1.5 to 1.8 days). Except fever, cough was the most common symptom (n=792, 78.9%), followed by rhinorrhea in 407 patients (40.5%). Rales and wheezing were detected in 16 patients (1.6%) and 19 (1.9%), respectively. Significant differences were observed for the number of patients who had cough, headache, vomiting, and wheezing among the three groups (P<0.05).

Conclusion

Although the incidence of cough, headache, vomiting, and wheezing differed significantly among the three groups, the number of patients in each group was too different to compare the results.

Keywords: Influenza A (H1N1), Seasonal Influenza A, Seasonal Influenza B

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Table 1.

Monthly Distribution of the Influenza Viruses

Mo/Yr	Influenza A (H1N1)	Influenza A (other)	Influenza B	Total
Sep./09	14 (1.4)	2 (0.2)	0 (0)	16
				(1.6)
Oct./09	220 (21.9)	4 (0.4)	1 (0.1)	225
				(22.4)
Nov./09	524 (52.2)	32 (3.2)	1 (0.1)	557
				(55.5)
Dec./09	164 (16.3)	2 (0.2)	1 (0.1)	167
				(16.6)
Jan./10	21 (18.4)	1 (0.1)	9 (0.9)	31
				(3.1)
Feb./10	1 (0.1)	1 (0.1)	6 (0.6)	8
				(0.8)
Total	944 (94.0)	42 (4.2)	18 (1.8)	1,004
				(100)

Values are presented as no. of positive cases (%).

Table 2.

Age, Sex Distribution and Fever Duration before Reverse Transcription-Polymerase Chain Reaction

	Influenza A(H1N1) (n=944)	Influenza A(other) (n=42)	Influenza B (n=18)	Total (n=1,004)	P -value
Sex, M: F	533:411 (1.3:1)	29:13 (2.2:1)	9:9 (1:1)	571:433 (1.3:1)	–
Age, yr (range)	7.0 (6.8–7.3)^∗	6.4 (4.9–7.8)^∗	6.7 (4.6–8.9)^∗	6.9 (5.9–7.4)^∗	0.558
Fever, day (range)	1.6 (1.5–1.7)^∗	1.7 (1.2–2.2)^∗	2.8 (2.1–3.4)^∗	1.6 (1.5–1.8)^∗	0.000^†

^∗ Values are presented as 95% confidence interval.

^† By Kruskal-Wallis test among 3 groups.

Table 3.

Percentage of Symptoms and Signs in 3 Groups

Symptoms & sings	Patients	Influenza A(H1N1) n=944 (%)	Influenza A(other) n=42 (%)	Influenza B n=18 (%)	Total n (%)	P-value^∗
Cough	Overall	756 (80.1)	23 (54.8)	13 (72.2)	792 (78.9)	<0.0001
	Subgroup	756 (80.1)	23 (54.8)	–	779 (80.0)	<0.0001
		756 (80.1)	–	13 (72.2)	769 (79.9)	0.381
		–	23 (54.8)	13 (72.2)	36 (59.4)	0.408
Rhinorrhea	Overall	385 (40.8)	14 (33.3)	8 (44.4)	407 (40.5)	0.614
	Subgroup	385 (40.8)	14 (33.3)	–	399 (40.5)	0.422
		385 (40.8)	–	8 (44.4)	393 (40.9)	0.811
		–	14 (33.3)	8 (44.4)	22 (36.7)	0.560
Sore throat	Overall	227 (24.0)	7 (16.7)	8 (44.4)	242 (24.1)	0.074
	Subgroup	227 (24.0)	7 (16.7)	–	234 (23.7)	0.354
		227 (24.0)	–	8 (44.4)	235 (24.4)	0.055
		–	7 (16.7)	8 (44.4)	15 (25.0)	0.048
Headache	Overall	178 (18.9)	4 (9.5)	7 (38.9)	189 (18.8)	0.034
	Subgroup	178 (18.9)	4 (9.5)	–	182 (18.5)	0.156
		178 (18.9)	–	7 (38.9)	185 (19.2)	0.061
		–	4 (9.5)	7 (38.9)	11 (18.3)	0.012
Vomiting	Overall	59 (6.3)	8 (19.0)	3 (16.7)	70 (7.0)	0.003
	Subgroup	59 (6.3)	8 (19.0)	–	67 (6.8)	0.005
		59 (6.3)	–	3 (16.7)	62 (6.4)	0.104
		–	8 (19.0)	3 (16.7)	11 (18.3)	1.000
Abdominal pain	Overall	50 (5.3)	1 (2.4)	0 (0)	51 (5.1)	0.707
	Subgroup	50 (5.3)	1 (2.4)	–	51 (5.2)	0.731
		50 (5.3)	–	0 (0)	50 (5.2)	0.626
		–	1 (2.4)	0 (0)	1 (1.7)	0.707
Diarrhea	Overall	22 (2.3)	1 (2.4)	0 (0)	23 (2.3)	1.000
	Subgroup	22 (2.3)	1 (2.4)	–	23 (2.3)	1.000
		22 (2.3)	–	0 (0)	22 (2.3)	1.000
		–	1 (2.4)	0 (0)	1 (1.7)	1.000
Dyspnea	Overall	8 (0.9)	0 (0)	0 (0)	8 (0.8)	1.000
	Subgroup	8 (0.9)	0 (0)	–	8 (0.8)	1.000
		8 (0.9)	–	0 (0)	8 (0.8)	1.000
		–	0 (0)	0 (0)	0 (0)	–
Seizure	Overall	4 (0.4)	0 (0)	0 (0)	4 (0.4)	1.000
	Subgroup	4 (0.4)	0 (0)	–	4 (0.4)	1.000
		4 (0.4)	–	0 (0)	4 (0.4)	1.000
		–	0 (0)	0 (0)	0 (0)	–
Rales	Overall	14 (1.5)	1 (2.4)	1 (5.6)	16 (1.6))	0.159
	Subgroup	14 (1.5)	1 (2.4)	–	15 (1.5)	0.482
		14 (1.5)	–	1 (5.6)	15 (1.6)	0.249
		–	1 (2.4)	1 (5.6)	2 (3.3)	0.514
Wheezing	Overall	14 (1.5)	2 (4.8)	3 (16.7)	19 (1.9)	0.001
	Subgroup	14 (1.5)	2 (4.8)	–	16 (1.6)	0.146
		14 (1.5)	–	3 (16.7)	17 (1.8)	0.003
		–	2 (4.8)	3 (16.7)	5 (8.3)	0.154

Values are presented as no. of positive cases (%).

^∗ By Fisher's exact test among groups; This is a retrospective study, and therefore significance level of alpha was not adjusted for multiple testing.

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