Purpose of review 

Neuraminidase inhibitor resistant influenza virus has recently emerged, and circulated, in untreated persons. Influenza virus evolution is causing antiviral susceptibility to change. We review the latest research in this rapidly moving field.

Recent findings 

Oseltamivir-resistant influenza H1N1 emerged globally, without drug selection pressure, during the 2007–2008 northern hemisphere influenza season. This unexpected event, coupled with reports of reducing susceptibilities of influenza B and H5N1, contradicts our understanding of the properties of neuraminidase inhibitor resistant influenza viruses. Knowledge of the structure of the neuraminidases and impact of mutations on drug binding has now expanded. Surveillance and clinical studies have identified key areas which require focused research such as the incidence of resistance in children and immunocompromised populations and the need for improved methodologies for detecting resistant virus on an individual and population level.

Summary 

Neuraminidase inhibitors, oseltamivir in particular, are the drugs of choice against seasonal influenza, zoonotic H5N1 and are stockpiled as the primary mitigating strategy for pandemic influenza containment and control. Further clinical and animal studies are essential to fully understand the capacity of neuraminidase inhibitor resistant influenza to be tolerated in the virus population, whilst retaining virulence and transmissibility. Vigilance, policy review and development of new anti-influenza drugs are essential.