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.