Antiviral resistance in influenza viruses circulating in Central and South America based on the detection of established genetic markers

Background Recent influenza antiviral resistance studies reveal an alarming increase in both adamantanes and neuraminidase inhibitors (NAIs) resistant viral strains worldwide, particularly in Asia, Europe and the United States. Objectives In this study, we have evaluated influenza virus resistance in Central and South America. Methods Influenza viruses, isolated from symptomatic patients throughout Central and South America in 2005–2008 were analyzed for inhibitor resistance. The M2 and NA genes of influenza viruses were sequenced and resistance was inferred by comparison with published sequences and known resistant mutations. Results Our results indicate that: (i) resistance to adamantanes was seen in the majority (95·5%) of the influenza A/H3N2 isolates but only in one isolate of the influenza A/H1N1 viruses; (ii) resistance to NAIs began to be detected in A/H1N1 isolates from Central America in 2008; and (iii) none of the influenza B viruses analyzed were resistant to NAIs. Conclusions These findings suggest a limited effectiveness of influenza inhibitors due to the detection of resistance among A/H1 and A/H3 viruses.