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From tomorrow's MMWR"

For the weeks ending October 4–December 6, WHO and NREVSS collaborating laboratories in the United States tested 24,906 respiratory specimens for influenza viruses; 6,751(27.1%) were positive. During the same period, the weekly percentages of respiratory specimens testing positive for influenza viruses increased from 1.4% to 37.1%. During the 2000–01, 2001–02, and 2002–03 influenza seasons, the peak percentages of specimens testing positive for influenza ranged from 23.2% to 26.4%. During the 1999–00 influenza season, when influenza A (H3N2) viruses predominated, the peak weekly percentage of specimens testing positive was 30.9%(1; CDC, unpublished data, 2003). Of the 6,751 positive isolates, 6,716 (99.5%) were influ-enza A viruses, and 35 (0.5%) were influenza B viruses. Ofthe 6,716 influenza A viruses, 1,255 (18.7%) have been subtyped; 1,254 (99.9%) were influenza A (H3N2) viruses, and one (0.1%) was an influenza A (H1) virus. As of Decem-ber 6, a total of 47 states and all nine surveillance regions had reported laboratory-confirmed influenza. CDC has characterized antigenically 215 influenza viruses that were collected and submitted by U.S. laboratories since
October 1. Of these, 212 were influenza A (H3N2) viruses,
and one was an influenza A (H1) virus. Of the 212 influ-enza
A (H3N2) viruses, 54 (25%) were similar antigenically
to the vaccine strain A/Panama/2007/99 (H3N2), which is
contained in this season’s vaccine, whereas 158 (75%) were
similar antigenically to A/Fujian/411/2002, a drift variant
of A/Panama/2007/99.