CDC Reports Seasonal Rise in Influenza Activity

Influenza A represents 84 percent of cases this season

MONDAY, Feb. 11 (HealthDay News) -- Despite a slow beginning, seasonal flu activity has increased sharply in recent weeks, consistent with the pattern of previous years, according to a statement issued this week from the U.S. Centers for Disease Control and Prevention (CDC).

According to the CDC, at present 31 states report widespread influenza activity, 17 report regional activity and two states plus the District of Columbia report local activity. In addition, deaths attributable to pneumonia and influenza have risen during the last month, indicating the expected seasonal upward trend.

Eighty-four percent of the influenza viruses typed in the CDC laboratory's surveillance systems are influenza A viruses, with the remaining 16 percent influenza B viruses. Over half of the influenza A viruses are of the H1N1 strain, which should be well covered by this year's vaccine. However, the H3N2 strain of influenza A viruses, and the type B viruses, may not be optimally covered, according to Joe Bresee, M.D., chief of the epidemiology and prevention branch of the CDC's influenza division.

It is "important to remember that while a less-than-ideal virus match between the viruses in the vaccine and those in the circulating viruses can reduce vaccine effectiveness, we know from past influenza studies that the vaccine can still protect enough to make illness milder or prevent flu-related complications," said Bresee.

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