Oseltamivir Resistance: What Does It Mean Clinically?

Public health officials, infectious disease specialists, and the world's population at large are girding their loins for the next influenza season. The winter months portend outbreaks, if not pandemics, of infections caused by both the seasonal influenza A virus subtype H3N2 and the novel influenza A virus subtype H1N1 or swine-origin virus. The swine-origin virus has never entirely gone away since its emergence last season and has manifested itself as a smoldering pandemic that refuses to die down but which has thankfully also not yet flared up, as the most virulent of influenza pandemics do. Accelerated efforts are under way to produce, test, and distribute vaccines against the “usual suspects”, as well as a vaccine directed at the novel H1N1 variant. However, in the absence of a vaccine, there has been universal reliance on the neuraminidase inhibitors for prophylaxis and treatment of presumed and proven novel H1N1 virus infection. Physicians and occupational health clinics in medical facilities have been faced with a number of conundrums related to the administration of neuraminidase inhibitors, primarily oseltamivir, to high-risk patients with influenza-like illness or to health care workers exposed to patients with influenza-like illness. Only now, after some health care workers have received multiple courses of oseltamivir because of repeated influenza-like illness exposures, has the futility of this approach, to say nothing of its propensity to select for resistance, become clear.