Clinical features of influenza C virus infection in children.
BACKGROUND
Seroepidemiological studies have revealed that influenza C virus is widely distributed globally. However, because the isolation of this virus is difficult, there have been few reports on its clinical features.


METHODS
Between December 1990 and November 2004, 84,946 respiratory-tract specimens were obtained from patients < or = 15 years old. On the basis of the results of isolation of virus, we examined the clinical data on children infected with influenza C virus.


RESULTS
Of 170 children infected with influenza C virus, 157 (92.4%) were < 6 years old. Fever (frequency, 90.0%), cough (frequency, 74.1%), and rhinorrhea (frequency, 61.8%) were the most frequent symptoms. The mean duration of fever was 2.88 days (standard deviation, 1.66 days). Of the 170 children, 29 were hospitalized, and 21 (72.4%) of these 29 had lower-respiratory-tract illness such as pneumonia, bronchitis, and bronchiolitis. The rate of hospital admission was significantly higher in children < 2 years old than in children 2-5 years old (30.4% vs. 11.9%; P = .0043).


CONCLUSIONS
Influenza C virus is a significant cause of upper-respiratory-tract illness in children < 6 years old, and the risk of complications with lower-respiratory-tract illness is particularly high in children < 2 years old.
Department of Infectious Diseases, Yamagata University School of Medicine, Iida-Nishi, Yamagata, Japan. matuzaki@med.id.yamagata-u.ac.jp
Yoko
Y
Matsuzaki
Noriko
N
Katsushima
Yukio
Y
Nagai
Makoto
M
Shoji
Tsutomu
T
Itagaki
Michiyo
M
Sakamoto
Setsuko
S
Kitaoka
Katsumi
K
Mizuta
Hidekazu
H
Nishimura
D000293:Adolescent; D002648:Child; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology* / Q000821:virology; D009982:Gammainfluenzavirus / Q000302:isolation & purification*; D008969:Molecular Sequence Data; D012141:Respiratory Tract Infections / Q000175:diagnosis* / Q000453:epidemiology* / Q000821:virology; D012621:Seasons