SURVEILLANCE OF OSELTAMIVIR-RESISTANT INFLUENZA A(H1N1)PDM09 IN GUANAJUATO STATE, MEXICO FROM 2009 TO 2012

Background: The influenza A(H1N1)pdm09 virus was first identified in Mexico in April 2009, subsequently spreading worldwide. Soon after the WHO declared a pandemic, a series of cases involving oseltamivir-resistant viruses were described, following concerns about the spread of strains resistant to neuraminidase inhibitors that could hamper control measures. To study the prevalence of oseltamivir-resistant influenza A(H1N1)pdm09, we implemented a surveillance program across the state of Guanajuato, Mexico. Methods: We collected respiratory samples from patients with confirmed infection with influenza A(H1N1) pdm09 virus between 2009 and 2012 in rural and urban regions in Guanajuato, Mexico. Specimens were screened for the H275Y mutation by Sanger sequencing. Results: A total of 1,192 laboratory confirmed influenza A(H1N1)pdm09-positive samples were processed between 2009 and 2012. Using two endpoint real-time polymerase chain reaction, 575 samples were sequenced. Two different clusters, I and II, were identified. The H275Y substitution was found in only one sample from cluster I. Conclusions: The prevalence of oseltamivir-resistant influenza A(H1N1)pdm09 2009 viruses during the pandemic period and following years was very low in our State.