FRIDAY, April 14, 2017 -- This year's flu season is rapidly winding down and is expected to end within the next couple of weeks, U.S. health officials predicted Friday.
It was a year much like the past few flu seasons, when the H3N2 virus was the most prevalent strain. That strain usually is hardest on the elderly and the very young.
But this flu season there was a slight twist -- middle-aged people were more affected than children, said Lynnette Brammer, an epidemiologist with the U.S. Centers for Disease Control and Prevention.
"We are not done yet, there's still flu out there, but it is declining," she said. "This is the first week that influenza A and B are both going down."
The 2016-2017 season followed a typical course, Brammer said. "We had a large wave of influenza H3N2 and then we had a smaller wave of influenza B at the end -- not an uncommon pattern," she said.
However, the really young seemed to be less affected than in a typical H3N2 year, Brammer said. "The hospitalization rates for 50- to 64-year-olds was higher than infants to 4-year-olds. We haven't seen that before in an H3N2 year," she said.
In a typical flu season, flu complications -- including pneumonia -- send more than 200,000 Americans to the hospital. Death rates fluctuate annually, but have gone as high as 49,000 in a year, according to the CDC.
This season, 72 children have died from flu complications, the CDC said.
In a typical flu season, an estimated 100 U.S. children die of complications from the disease.
While this year's vaccine was well-matched against the circulating strains, it was about 48 percent effective, Brammer said. That means those who were vaccinated had about a 50 percent chance of avoiding the flu.
"It is not as good as we would like, but for an H3N2 predominant year, that's good," Brammer said.
Typically, the flu vaccine is between 50 and 60 percent effective, although the level of protection varies by the strain of the viruses. The vaccine is usually less effective against the H3N2 strain, Brammer said.
Although the flu season is all but over in the Northern Hemisphere, it's just ramping up in the Southern Hemisphere, so if you are traveling there it's a good idea to get vaccinated, she said.
Next year's vaccine is based on the flu strains now circulating in the Southern Hemisphere, Brammer said. It appears that the same H3N2 and B viruses that were seen this year will be the predominant strains next season. The only change to the 2017-18 vaccine is a tweak to the H1N1 component to take into account a genetic change in that virus, she said.
Next season's vaccine will become available in September, then "we start the cycle over again," Brammer said.
To learn more about flu, visit the U.S. Centers for Disease Control and Prevention.
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