title: Longer virus shedding in influenza B than in influenza A among outpatients treated with oseltamivir.
abstract: 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.
authors.affiliation: 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>
authors.forename: Naoki
authors.initials: N
authors.lastname: Kawai
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Ikematsu
authors.forename: Norio
authors.initials: N
authors.lastname: Iwaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawashima
authors.forename: Tetsunari
authors.initials: T
authors.lastname: Maeda
authors.forename: Satoru
authors.initials: S
authors.lastname: Mitsuoka
authors.forename: Kunio
authors.initials: K
authors.lastname: Kondou
authors.forename: Ietaka
authors.initials: I
authors.lastname: Satoh
authors.forename: Kiyomitsu
authors.initials: K
authors.lastname: Miyachi
authors.forename: Shigeru
authors.initials: S
authors.lastname: Yamaga
authors.forename: Takeshi
authors.initials: T
authors.lastname: Shigematsu
authors.forename: Nobuo
authors.initials: N
authors.lastname: Hirotsu
authors.forename: Seizaburo
authors.initials: S
authors.lastname: Kashiwagi
mesh_terms: 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
chemical_list: D000998:Antiviral Agents; D053139:Oseltamivir