According to updates and reports by the CDC, the 2013-2014 flu season is the worst in the U.S. since 2009 — especially among young and middle-aged adults younger than 65.
The CDC reported that 60 percent of hospitalizations for influenza this flu season have been of people between the ages of 18-64, whereas over the past year, this age category only made up 35 percent of influenza cases.
A follow-up report by the Los Angeles Times estimated that 34 percent of people between 18 and 64 are receiving annual vaccination — the lowest of any age demographic.
In an interview with NPR, Dr. Cameron Wolfe, an assistant professor of infectious disease at Duke, said the reason for the high number of young and middle-aged adults sick with influenza is that they believe themselves healthy enough to not need the annual flu vaccine.
"Very young teenagers and college-age kids tend to think they're immortal," Wolf said to NPR. "And I think there's a general misunderstanding of the role of vaccines."
This year's flu strain — the H1N1 virus, or swine flu — has been quite deadly so far. In California, where the virus has been strong, 278 people have died from influenza-caused symptoms, according to a Feb. 21 press release from the California Department of Public Health.
Wolfe said part of the misunderstanding is that flu vaccines take up to two weeks to take full effect, and if someone gets sick after they've received the vaccine but before it can take effect, that person can mistakenly believe the vaccine either didn't work or made them sick.
Pregnant women also have a high risk of contracting the flu virus, according to the CDC.
In a Feb. 11 story, CNN reported that a 29-year-old Arkansas woman who was 20 weeks pregnant contracted the virus, lost the baby and then died herself three weeks later from flu symptoms.
To combat the high number of young and middle-aged adults contracting the swine flu, Dr. Tom Frieden, director of the CDC, has some advice all Americans can still take: Get the vaccine.
According to the CDC, the flu season could likely continue through April.