Longer virus shedding in influenza B than in influenza A among outpatients treated with oseltamivir.
OBJECTIVE
To compare the persistence, susceptibility and resistance of influenza A and influenza B viruses in oseltamivir therapy in outpatients of various ages.


METHODS
Virus isolation was done before and 4-6 days after the initiation of oseltamivir therapy for 148 patients with influenza A/H3N2 and for 66 with influenza B in the 2003-2004 and 2004-2005 influenza seasons. Neuraminidase inhibition assay and neuraminidase or hemagglutinin sequence analysis were done using influenza viruses isolated from these patients.


RESULTS
The virus isolation rate after oseltamivir therapy was significantly higher for influenza B (33.3%) than for influenza A/H3N2 (12.8%, p<0.001). The mean IC(50) values before and after oseltamivir therapy were significantly higher in patients with influenza B (10.82 and 11.32nM, respectively) than in patients with influenza A/H3N2 (0.94 and 0.81nM, respectively, both p<0.001). No significant differences in IC(50) among each age group, or no significant increase in IC(50) from before to after oseltamivir therapy was observed. Neuraminidase or hemagglutinin sequence analysis revealed no known genotype with resistance to oseltamivir.


CONCLUSIONS
Virus persistence after oseltamivir therapy was longer and IC(50) values were higher in influenza B than influenza A.
Kawai
Naoki
N
Japan Physicians Association, Tokyo Medical Association Building 3F, Kanda-Surugadai, Chiyoda-ku, Tokyo, Japan. nkawai@city.gifu.med.or.jp <nkawai@city.gifu.med.or.jp>
Ikematsu
Hideyuki
H
Iwaki
Norio
N
Kawashima
Takashi
T
Maeda
Tetsunari
T
Mitsuoka
Satoru
S
Kondou
Kunio
K
Satoh
Ietaka
I
Miyachi
Kiyomitsu
K
Yamaga
Shigeru
S
Shigematsu
Takeshi
T
Hirotsu
Nobuo
N
Kashiwagi
Seizaburo
S
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000998:Antiviral Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D002648:Child; D002675:Child, Preschool; D024882:Drug Resistance, Viral / Q000235:genetics; D005260:Female; D006801:Humans; D007223:Infant; D053122:Influenza A Virus, H3N2 Subtype / Q000187:drug effects / Q000502:physiology*; D009981:Influenza B virus / Q000187:drug effects / Q000502:physiology*; D007251:Influenza, Human / Q000188:drug therapy* / Q000821:virology; D020128:Inhibitory Concentration 50; D008297:Male; D008875:Middle Aged; D053139:Oseltamivir / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D017201:Virus Shedding
D000998:Antiviral Agents; D053139:Oseltamivir