This overview of the current status of the 2009 H1N1 influenza pandemic in the U.S. describes the epidemiology, clinical manifestations, and treatment of individuals infected with 2009 H1N1 influenza. Information is current as of October 21, 2009.

Two studies published ahead of print in the New England Journal of Medicine provide evidence that a single dose of vaccine may be sufficient for the 2009 H1N1 influenza A.

As the world is currently in the midst of a WHO stage VI pandemic with the 2009 H1N1 influenza virus, it remains a possibility that this virus could reassort with other flu strains--most notably, the WHO stage III pandemic H5N1 avian influenza virus.

Antiviral therapy against influenza always has been plagued by the development of resistance. Unfortunately, as medical mngmnt of flu relies increasingly on antiviral therapy, resistance will become more commonplace, and may render some drugs obsolete.

A new H3N2 variant has emerged that may be poorly matched to the 2009 seasonal flu vaccine. This could pose a risk to the elderly and to those who have been vaccinated against the pandemic strain.

Several scientific papers have been published recently that elucidate both the spectrum of illness caused by the 2009 H1N1 influenza (A) virus and its ability to evade antiviral drugs.

There have been cases of the 2009 H1N1 influenza (A) virus among healthcare workers, as detailed in the June 19, 2009 MMWR. It appears that all could have been prevented had standard infection control measures been taken.

However, the pandemic potential of the H7 viruses cannot be overlooked. While they are not nearly as lethal as H5N1, a pandemic need not cause mass lethality to have a significant impact around the globe.