Mutated influenza A(H1N1) 2009 detected in Norway

The Norwegian Institute of Public Health reported today that it detected an unusual mutation in three individuals; two of whom were the first fatal cases of influenza A (H1N1) 2009 in the country, and one of whom has severe illness.

The Norwegian Institute of Public Health reported on these detections, as did WHO (also see links to reports below). The Norwegian public health agency subsequently analyzed isolates from more than 70 patients infected with influenza A (H1N1) 2009 who manifested clinical illness, and no further instances of mutation were detected. These findings suggest that the mutation is not widespread in the country.

WHO reports that worldwide, laboratory monitoring of influenza viruses has detected a similar mutation in viruses from several other countries (with the earliest detection occurring in April), including Brazil, China, Japan, Mexico, Ukraine, and the US. No evidence currently suggests these mutations are leading to an unusual increase in the number of H1N1 2009 infections or a greater number of severe or fatal cases.

Dr. Anne Schuchat of the U.S. Centers for Disease Control and Prevention mentioned in a media briefing today that while this mutated virus is unusual, it sporadically has been detected in the US, though typically associated with more mild disease.

What are the implications of viral mutation?

• Viral mutations are normal; this specific mutation detected by the Norwegian Institute of Public Health probably will be of little or no importance (per Norwegian Institute of Public Health).
• This specific viral mutation is associated with the virus's virulence and ability to live deeper in respiratory tissue.
• Current data suggest this viral mutation has no implications for pandemic influenza A (H1N1) vaccine match or antiviral efficacy.
• The public health implications of this mutation are unclear, and may be difficult to assess (per WHO and Dr. Schuchat). It is important to note, however, that WHO reports there is no current evidence suggesting this mutation is leading to an unusual increase in the number of H1N1 2009 infections or a greater number of severe or fatal cases.
• To date, no links between the small number of patients infected with the mutated virus have been found, and the mutation doesn't appear to be spreading.

Sources:

Norwegian Institute of Public Health: http://www.fhi.no/eway/default.aspx?pid=233&trg=MainLeft_5669&MainLeft_5669=5544:81363::0:5667:1:::0:0

WHO: http://www.who.int/csr/disease/swineflu/notes/briefing_20091120/en/index.html

CDC media briefing: http://www.cdc.gov/media/transcripts/2009/t091112.htm