Effects of oseltamivir treatment on duration of symptoms and viral shedding, and household transmission of influenza virus
Session VII – Cowling, Benjamin – Abstract 3 of 3
Title of Contribution: Effects of oseltamivir treatment on duration of symptoms and viral shedding, and household transmission of influenza virus
Author(s): S Ng1, BJ Cowling1, KY Cheng1, VJ Fang1, KH Chan2, TM Uyeki3, PM Houck4, JSM Peiris2, GM Leung1
Affiliation(s): 1Department of Community Medicine and School of Public Health, the University of Hong Kong; 2Department of Microbiology, the University of Hong Kong; 3Influenza Branch, National Center for Infectious Diseases, CDC; 4Division of Global Migration and Quarantine, National Center for Infectious Diseases, CDC.
Abstract:
Background: Several large controlled trials have demonstrated that antivirals can reduce the duration and severity of illness if taken sufficiently early after symptoms begin. However there are few estimates of the degree to which antivirals reduce the transmissibility of influenza. We assessed the effect of antiviral use on clinical disease and infectivity as part of a large community study of influenza transmission in households in Hong Kong.
Methods: Subjects with confirmed influenza virus infection by the QuickVue Influenza A+B rapid test were recruited from 30 outpatient clinics in Hong Kong during the 2008 influenza season. Nose and throat swabs were collected from all household members at an initial home visit within 36 hours of recruitment and 3 and 6 days later, to determine influenza virus infection by RT-PCR. Clinical influenza in secondary contacts was assessed by self-reported symptom diaries.
Results: A total of 322 index cases and their households were recruited in 2008. Index cases without PCR-confirmed influenza and index cases prescribed antivirals other than oseltamivir were excluded. Symptom scores were not statistically significantly different (p=0.29) at baseline between the index cases prescribed oseltamivir (mean score 4.71) and the index cases not prescribed an antiviral (mean score 4.50). The oseltamivir group showed lower daily total symptom score from day 1 after recruitment and the difference was statistically significant from day 3 onwards. The oseltamivir group had shorter duration of viral shedding and their household contacts were less likely to develop RT-PCR-confirmed infection (secondary attack ratio, SAR 14%) versus contacts of index cases not prescribed an antiviral (SAR 22%).
Discussion: Our results are consistent with previous controlled trials that oseltamivir treatment is effective in reducing the severity and duration of clinical symptoms of index cases. Our results are inconclusive on the role of oseltamivir treatment in preventing household influenza transmission.
