Tamiflu-resistance Emerging
Update
By Carol A. Kemper, MD, FACP, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, Section Editor, Updates; Section Editor, HIV, is Associate Editor for Infectious Disease Alert.
ProMED-mail post, January 29 and January 31, 2008; www.promedmail.org
World health authorities and the European equivalent of the CDC alerted doctors and the public that Influenza A strains circulating in Europe this winter appear to be increasing resistance to oseltamivir (Tamiflu). Previously, oseltamivir-resistant strains occurred with less than 1% frequency. However, as part of a general surveillance program, 437 isolates of Influenza A (H1N1) identified in ten European countries from November 2007 to January 2008 were tested; 14% showed evidence of resistance to oseltamivir. All of the isolates appear to carry the same amino acid substitution (H274Y) of the neuraminidase, which is known to cause high-level oseltamivir resistance. The oseltamivir-resistant strains remained sensitive to zanamivir (Relenza) and amantadine/rimantidine.
The proportion of resistant isolates was greatest in isolates from Norway. Of 37 Norwegian isolates, 26 (70%) were oseltamivir-resistant. Data indicate the isolates were transmitted within that country. Resistant isolates were also detected in France (17% of isolates), Germany (7%), the United Kingdom (5%), and Belgium. Other surveillance data from 16 European countries this winter indicate that 81% of influenza isolates this year are Influenza A. The predominant circulating strain is similar to A/Solomon Islands/3/2007, which is included in the 2007-2008 flu vaccine. Experts are puzzled over this sudden jump in oseltamivir resistance, especially in Norway, where it is believed there has been minimal selective pressure from infrequent use of Tamiflu.
World health authorities and the European equivalent of the CDC alerted doctors and the public that Influenza A strains circulating in Europe this winter appear to be increasing resistance to oseltamivir (Tamiflu). Previously, oseltamivir-resistant strains occurred with less than 1% frequency.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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