CDC last week announced that this year's influenza outbreak has reached epidemic levels.
According to the New York Times' "The Upshot," the flu reaches "epidemic" status almost every year, but experts say it has reached it unusually early in the season this year.
In early December, CDC officials warned that the year's flu season could result in more fatalities than other years. CDC Director Tom Frieden noted that the dominant flu strain circulating this year, H3N2, tends to lead to a greater number of hospitalizations and fatalities than other strains. Further, about half of the flu samples tested in the early stages of this year's flu season were a new H3 subtype of the virus that this year's vaccine is not well prepared to fight.
This year's influenza season so far has hospitalized more U.S. patients than in recent years, raising concerns that it could be a more severe outbreak than in the past.
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According to the Wall Street Journal, the hospitalization rate for all patients so far is 9.7 people per 100,000, compared with 4.3 people per 100,000 last year and 5.5 people per 100,000 the year before that. Meanwhile, 15 children ages 18 and younger have died from the flu as of Dec. 20, compared with four deaths around the same time in 2013.
Currently, 36 states are experiencing high levels of flu activity, CDC reports. Google Flu Trends data note that the flu has been spreading faster in the Southeast and Midwest, with Dayton, Ohio, and Knoxville, Tenn., experiencing some of the highest flu activity.
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According to the "The Upshot," the high rate of flu diagnoses can be attributed to:
- The early start of this year's flu season;
- The H3N2 flu strain that makes people sicker;
- A relatively low vaccination rate; and
- Vaccinations that do not match the H3N2 flu strain.
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Michael Jhung, a medical officer in CDC's flu division, acknowledges the severity of the current flu season but also notes that it is too soon to determine whether it will be worse than those of prior years. "We never know how this season compares to the previous season until the end of the year," he says (Sanger-Katz, "The Upshot," New York Times, 12/30/14; Armour/Bauerlein, Wall Street Journal, 12/30/14).