Short report

Modeling the effects of drug resistant influenza virus in a pandemic

Stefan O Brockmann¹ , Markus Schwehm² , Hans-Peter Duerr² , Mark Witschi³ , Daniel Koch³ , Beatriz Vidondo³ and Martin Eichner²

¹Department of Epidemiology and Health Reporting, Baden-Württemberg State Health Office, District Government Stuttgart, Germany

²Department of Medical Biometry, University of Tübingen, Germany

³Swiss Federal Office for Public Health, Bern, Switzerland

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Virology Journal 2008, 5:133doi:10.1186/1743-422X-5-133

Published:	30 October 2008

Abstract

Neuraminidase inhibitors (NI) play a major role in plans to mitigate future influenza pandemics. Modeling studies suggested that a pandemic may be contained at the source by early treatment and prophylaxis with antiviral drugs. Here, we examine the influence of NI resistant influenza strains on an influenza pandemic. We extend the freely available deterministic simulation program InfluSim to incorporate importations of resistant infections and the emergence of de novo resistance. The epidemic with the fully drug sensitive strain leads to a cumulative number of 19,500 outpatients and 258 hospitalizations, respectively, per 100,000 inhabitants. Development of de novo resistance alone increases the total number of outpatients by about 6% and hospitalizations by about 21%. If a resistant infection is introduced into the population after three weeks, the outcome dramatically deteriorates. Wide-spread use of NI treatment makes it highly likely that the resistant strain will spread if its fitness is high. This situation is further aggravated if a resistant virus is imported into a country in the early phase of an outbreak. As NI-resistant influenza infections with high fitness and pathogenicity have just been observed, the emergence of drug resistance in treated populations and the transmission of drug resistant strains is an important public health concern for seasonal and pandemic influenza.