H1N1 Mutations No Cause for Alarm

December 1, 2009

Although the future clinical implications of mutations in the H1N1 influenza virus remain unclear, these changes do not pose an immediate threat.


Although the future clinical implications of mutations in the H1N1 influenza virus remain unclear, these changes do not pose an immediate threat, said Dr Keiji Fukuda, special advisor on pandemic influenza to the World Heath Organization, at a recent press conference.

Two separate clusters of oseltamivir resistance were identified in the United States and the United Kingdom. The resistant viruses were found only in severely immunocompromised patients (eg, those with HIV infection or hematological cancer).

Much of the previously seen resistance was associated with prophylactic use of oseltamivir; these clusters occurred in patients who were treated with the antiviral. However, oseltamivir and zanamivir remain highly effective treatments for H1N1 infection when they are used early and appropriately, said Dr Fukuda.

A mutation identified in 3 Norwegian patients with severe disease has been the focus of recent attention. This mutation has also been found in the Ukraine, Brazil, China, Japan, Mexico and the United States, in both serious and mild cases. Investigators are currently trying to determine whether this mutation is associated with more severe disease and whether it is becoming more prevalent, said Dr Fukuda.