Pandemic (2009) H1N1 (also known as Novel or Swine-Origin) Influenza A Virus

Updated January 11, 2011

Mayo Medical Laboratories is committed to offering timely updates and information regarding laboratory testing options for influenza A. During 2009, much attention was given to the newly emergent pandemic (2009) H1N1 Influenza A virus, also known as novel or swine-origin influenza A. This virus arose in Mexico and very quickly spread throughout the world, gaining the highest level of Pandemic status (level 6) by the World Health Organization (WHO). After 2 separate peaks of disease, infection by the 2009 H1N1 virus has decreased and is no longer considered a pandemic threat by the WHO.

Now in the 2011 influenza season, H1N1 is co-circulating with a seasonal influenza A virus (H3N2) and is causing low to moderate levels of infection throughout the world. These infections fall within the expected levels of infection for influenza season.

For detection of both pandemic (2009) H1N1 and seasonal influenza A viruses, clients may order the Mayo Medical Laboratories #60551 Influenza Virus Type A and Type B, Molecular Detection by PCR. A panel is also available for simultaneous detection of Influenza A, B, and RSV by PCR (#60552 Influenza Virus Type A and Type B, and Respiratory Syncytial Virus (RSV), Molecular Detection, PCR).

These are the tests of choice for detecting acute illness with any of the influenza viruses. If the result is positive for influenza A, it indicates that influenza A is present in the sample, but it does not differentiate Pandemic (2009) H1N1 influenza from other seasonal influenza A subtypes.

Alternative Influenza Tests

Although alternative influenza A tests such as culture and serology are available, they are not recommended for primary detection of the pandemic (2009) H1N1 strain. Rapid antigen detection tests may be available to some clients in their own health care settings, but the sensitivity and specificity of these tests are highly variable, and confirmation of negative results using culture or PCR may be recommended.

To learn more about influenza A and the pandemic (2009) H1N1 strain, see:

• CDC H1N1 Web Site