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Flu no longer widespread in the U.S.

2:08 PM, Mar 1, 2013   |    comments
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by Elizabeth Weise, USA TODAY


Flu isn't totally gone, but we're on the downward slope, according to the latest report from the Centers for Disease Control and Prevention.

Influenza is no longer widespread nationwide. As of last week, 12 states reported widespread flu activity and 28 had flu cases regionally, according to the CDC's weekly FluView report issued Friday. The previous week, 22 states reported widespread activity and 21 regional cases. Widespread means that "flu is appearing throughout a state, cases are scattered all over the state rather than just in little pockets," said Lyn Finelli, CDC's chief of surveillance and outbreak response.

Right now the states with the most flu are in the Northeast and the West. Oregon and Nevada are bearing the brunt on the West Coast while in the Northeast, New York, New Jersey, Massachusetts, Pennsylvania, Michigan and Ohio all have lots of flu, Finelli said.

Nationally, 8.4% of deaths reported in CDC's 122 Cities Mortality Reporting System were due to pneumonia and influenza as of Feb. 23. The previous week it was 8.6%. That's still above the epidemic threshold of 7.2%.

The proportion of people visiting the doctor for influenza-like illness around the country is down to 2.7%, from 2.8% the week before. That's just slightly above the national baseline number, which is 2.2%. The baseline is calculated based on the amount of flu that circulates in the nation during non-flu periods such as summer.

The CDC won't declare this year's flu season finished until there have been several weeks of flu activity below that 2.2% baseline for several consecutive weeks, Finelli said.

So far 81 children have died as a result of the flu since the season's start. This is up from 78 deaths the previous week. Death rates for adults are not kept nationally.

Overall, this year's flu season was made of up three flu strains. Most cases were made up of two influenza A strains, the H2N3 subtype and a small amount of H1N1, the strain responsible for the 2009 global pandemic. Influenza B strains were also circulating.

The A strains are falling as the season wanes, but as often happens, the B strains are becoming more prevalent, Finelli said.

"Often in the springtime we get a sweep of B and it becomes the predominant virus," Finelli said. "That's an interesting finding and we'll keep our eye on it."

Hospitalization rates for influenza-like illnesses continue to rise, up to 36.7 people out of 100,000 as of last week. The previous week they were at 34.2.

Hospitalization tends to lag behind visits to doctors' offices, so the CDC expects them to stay high for a while. Rates of illnesses and hospitalization for those over 65 have remained quite high.

Last week the number of people in that age group hospitalized for flu-like illness was in the mid-160s out of every 100,000. The previous week it was 151 out of 100,000, Finelli said.

Overall in mild flu years only 3,000 Americans die from influenza-related causes, but in severe seasons it can go as high as 49,000, CDC statistics show.

This year has been dangerous for the elderly for three reasons. First, influenza is always more dangerous to people 65 and older because their immune systems are weaker. In addition, of the three major flu strains circulating in the United States this year the most prevalent one, H3N2, is especially dangerous to older people. Finally, the vaccine given to those over 65 wasn't very effective, health officials reported last week.

Although some people over 65 got a different vaccine from the rest of the population, that doesn't appear to be the reason behind the higher rates in those over 65, Finelli said.

Still, the company which makes the newer vaccine, Sanofi, is conducting studies of its effectiveness this year and should have results next year.

Copyright 2013 USATODAY.com

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