Flu (Influenza)

In the past several weeks, manufacturers have started shipping flu vaccines and expect to supply a record 143 million doses to the U.S.

Flu shots are being shipped earlier than usual this year to ensure that an adequate supply is in the hands of doctors, clinics and other providers by the end of October.

Another flu season is fast approaching. The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The best way to prevent the flu is by getting a flu vaccination each year.

Every year in the United States, on average:

• 5% to 20% of the population gets the flu;

• more than 200,000 people are hospitalized from flu complications, and;

Historical Analyses Help Plan for Future Pandemics

One of the persistent riddles of the deadly 1918 Spanish influenza pandemic is why it struck different cities with varying severity. Why were some municipalities such as St. Louis spared the fate of the hard-hit cities like Philadelphia when both implemented similar public health measures? What made the difference, according to two independent studies funded by the National Institutes of Health (NIH), was not only how but also how rapidly different cities responded.

CDC HEALTH ALERT: CDC Recommends against the Use of Amantadine and Rimantadine for the Treatment or Prophylaxis of Influenza in the United States during the 2005–06 Influenza Season

Recent evidence indicates that a high proportion of currently circulating Influenza A viruses in this country are resistant to these medications

January 14, 2006, 3:25 PM EST

While the primary strategy for preventing complications of influenza infections is annual vaccination, antiviral medications with activity against influenza viruses can be effective for the prophylaxis and treatment of influenza. Two classes of antivirals are currently available—the M2 ion channel inhibitors (i.e., the two adamantanes amantadine and rimantadine) and the neuraminidase inhibitors (i.e., oseltamivir and zanamivir). The neuraminidase inhibitors are effective for the treatment and prophylaxis of influenza A and B, while the adamantanes are only active against influenza A viruses. This alert provides new information about the resistance of influenza viruses currently circulating in the United States to the adamantanes, and it makes an interim recommendation that these drugs not be used during the 2005–06 influenza season. Amantadine is also used to treat the symptoms of Parkinson’s disease, and should continue to be used for this indication.

Viral resistance to adamantanes can emerge rapidly during treatment because a single point mutation at amino acid positions 26, 27, 30, 31, or 34 of the M2 protein can confer cross-resistance to both amantadine and rimantadine. The transmissibility of adamantane-resistant viruses is not impaired by any of these amino acid changes. A recent report on the global prevalence of adamantane-resistant influenza viruses showed a significant increase (from 1.9% to 12.3%) in drug resistance over the past 3 years. In the United States, the frequency of drug resistance increased from 1.9% in 2004 to 14.5% during the first 6 months of the 2004–05 influenza season.