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Signs are pointing to a tough flu season for the U.S. this year.
While influenza has not quite reached epidemic levels yet, it’s spreading farther and faster than it did at the same time last year, the Centers for Disease Control and Prevention said Friday.
Flu is already widespread in seven states: Arkansas, Georgia, Louisiana, Massachusetts, Mississippi, Oklahoma, and Virginia. During this same week in 2016, influenza was not widespread in any states.
And three states — Louisiana, Mississippi, and South Carolina — have high levels of flu already this year.
Influenza has already killed seven children this season, the CDC said. It killed at least 95 children in the 2016-2017 season, and the CDC found that at least three-quarters of kids who died from influenza between 2010 and 2014 had not been vaccinated in the months before they got sick.
Flu causes an epidemic every single year in the U.S. and most of the rest of the world. Flu is so common that health officials don’t count every single case. Instead, they calculate how bad flu is by the proportion of deaths that are shown to have been caused by pneumonia and influenza.
That number takes a few weeks to calculate but in the week that ended November 18, 5.7 percent of reported deaths were caused by pneumonia and influenza.
“This percentage is below the epidemic threshold of 6.6 percent for week 46,” the CDC said.
Related: Severe flu season looks possible
Influenza is a major killer.
“The United States alone sees 140,000 to 710,000 influenza-related hospitalizations and 12,000 to 56,000 deaths each year, with the highest burden of disease affecting the very young, the very old, and people with coexisting medical conditions,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, wrote in a commentary in the New England Journal of Medicine.
While the CDC recommends flu vaccine for everyone over the age of 6 months, the vaccine is not terribly effective and this year’s vaccine seems especially unpromising.
Each flu vaccine protects against either three or four different strains of flu, but one component, the H3N2 strain, seems especially weak. During Australia’s flu season just ended, the H3N2 component only provided about 10 percent protection against severe influenza, Fauci noted.
That doesn't mean the same is true for the U.S. Different flu strains may circulate here and the vaccine may be more effective.
Research published last month helps explain why flu vaccines often do not work so well: most influenza vaccines are produced in chicken eggs, and that process makes the virus mutate, thus making the vaccine produced using the virus less effective.
“Given that most of the U.S. influenza-vaccine supply is currently produced in eggs and the composition of the 2017–2018 Northern Hemisphere vaccine is identical to that used in Australia, it is possible that we will experience low vaccine effectiveness against influenza A (H3N2) viruses and a relatively severe influenza season if they predominate,” Fauci wrote.
Nonetheless, Fauci and other top health experts say it’s worth getting the vaccine.
“It is always better to get vaccinated than not to get vaccinated,” Fauci said. It’s more effective against the H1N1 and influenza B strains that are also spreading.
“In this regard, the CDC estimates that influenza vaccination averted 40,000 deaths in the United States between the 2005–2006 and 2013–2014 seasons,” Fauci wrote.
The good news is that the virus has not evolved resistance to the drugs, including Tamiflu, that can be used to treat influenza. People can also protect themselves and other from flu by washing their hands frequently and covering sneezes and coughs.