An observational study of influenza A(H1N1)pdm09 viral shedding and resistance under standard-duration oseltamivir treatment

An observational study was established in South Africa in 2009, early in the influenza A(H1N1)pdm09 outbreak, to provide information on the virological response of the new virus to oseltamivir and the potential for resistance. Patients (n = 54) aged 1-64 years who were treated with standard five-day courses of oseltamivir, starting within two days of onset of the symptoms, showed rapid reductions in viral load or shedding and clinical signs and symptoms. Oseltamivir was well tolerated, with no serious adverse events. Signs of treatment-emergent phenotypic and genotypic resistance were noted in one patient.