U.S.: 2008-2009 Influenza Season Week 48 ending November 29, 2008

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Excerpts:

Antiviral Resistance:

Since October 1, 2008, 25 influenza A (H1N1), five influenza A (H3N2), and nine influenza B viruses from 11 states have been tested for antiviral resistance; however, 72% of the viruses tested were from only two states. Twenty-four of 25 influenza A (H1N1) viruses tested were resistant to oseltamivir; while all 25 viruses were sensitive to zanamivir. All influenza A (H3N2) and B viruses tested were sensitive to oseltamivir and zanamivir.
Twenty-five influenza A (H1N1) and five influenza A (H3N2) viruses were tested for adamantane resistance. All influenza A (H1N1) viruses were sensitive to the adamantanes. All influenza A (H3N2) viruses tested were resistant to the adamantanes. The adamantanes are not effective against influenza B viruses.
Only one state has reported local influenza activity during the 2008-09 season in the United States to date, thus the number of virus specimens available for antiviral resistance testing is limited in both the overall number tested and in the number of states that have submitted specimens. Limited data on antiviral resistance, as well as the uncertainty regarding which influenza virus types or subtypes will circulate during the season, make it impossible to provide an indication of the prevalence of influenza viruses resistance to oseltamivir or the adamantanes (amantadine and rimantadine) nationally or regionally at this time. CDC has solicited a representative sample of viruses from WHO collaborating laboratories in the United States, and more specimens are expected as influenza activity increases.







Geographic Spread of Influenza as Assessed by State and Territorial Epidemiologists:


During week 48 the following influenza activity was reported:

• Local influenza activity was reported by one state (Hawaii).
• Sporadic activity was reported in Puerto Rico and 22 states (Alaska, Arizona, Arkansas, California, Colorado, Connecticut, Florida, Idaho, Indiana, Massachusetts, Maryland, Michigan, New Hampshire, New York, Oregon, Pennsylvania, Rhode Island, South Dakota, Texas, Utah, West Virginia, and Wisconsin).
• No influenza activity was reported in the District of Columbia and 27 states (Alabama, Delaware, Georgia, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maine, Minnesota, Mississippi, Missouri, Montana, Nebraska, Nevada, New Jersey, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, South Carolina, Tennessee, Vermont, Virginia, Washington, and Wyoming).