Why this year's flu season is so bad and what you can do about it

— -- The flu has ramped up early this year and is rapidly spreading across the country, with widespread flu activity in 46 states, according to the latest data from the U.S. Centers for Disease Control and Prevention.

"This is a feature of this year’s flu -- not only did it start early, but it seemed to occur all over the country more or less simultaneously," Dr. William Schaffner, infectious disease specialist at Vanderbilt University, told ABC News.

How bad is it?

The flu has not yet reached “epidemic” proportions, according to last week’s CDC data, but it may happen soon. A flu epidemic occurs when the percentage of people who have died from the flu exceeds a threshold set by the CDC using data from prior years. Last week, the number of people who died from the flu this year was only 0.2 percent below that threshold.

Doctor’s visits for flu-like illness are rising. This year’s numbers are almost identical to three years ago, in the 2014-2015 season -- both years surpassed what was seen last year, 2016-2017.

Twenty-six states are reporting high flu activity, with some of the worst in Arkansas, where 14 percent of outpatient doctor visits were for influenza-like illness last week. Neighboring states of Mississippi and Texas also have high flu activity, with 12 percent of doctors’ visits related to flu-like symptoms.

But when patients must be admitted to the hospital, flu can turn deadly. The number of patients in the hospital for flu-like illness nationally has doubled in the past two weeks and is higher than in recent years -- about 35 percent up from the same time last year. Most of the people who are hospitalized for the flu are over the age of 65.

The predominant flu strain this year is H3N2, a form of influenza A. This strain is included in this year’s flu vaccine, but information on how effective the vaccine has been is typically not available until the flu season is over.

Vaccine effectiveness typically ranges from 40 to 60 percent in a good year. Preliminary estimates from last year show the vaccine was 40 percent effective in the U.S., similar to 2014-2015.

Concerns have been raised about this year's vaccine after an editorial published in the New England Journal of Medicine last Thursday said it was only 10 percent effective against H3N2 in Australia.

Schaffner cautions against using this statistic to predict how well the vaccine will work in the U.S., since this is not official CDC data, but warns it could be a bad sign.

“We are being affected by the basically same virus and using basically the same vaccine,” he said.

Additionally, years in which H3N2 is the predominant influenza strain tend to have higher death rates, with approximately 20,000 deaths in the 2012-2013 and 2014-2015 seasons when H3N2 predominated.

The good news is that this year’s flu seems to be quite susceptible to the available flu medications, like Tamiflu, also known as oseltamivir. What’s more, Tamiflu, is “widely available” according to its manufacturers, who do not expect any shortage of the medication. It is most helpful if taken within 48 hours of the start of the flu.

Schaffner points out that the vaccine provides good protection against other influenza strains, which are becoming more common this season.

“It’s an imperfect vaccine, but it’s the best we have, and it still does provide a terrific amount of protection -- complete protection and partial protection,” he said. “You contribute to your own protection and a healthier community -- a community where there is less likelihood of spread.”

How the flu vaccine helps

First, get the vaccine -- there’s still time.

"It is late and so do not walk, run," said Schaffner. "Run to your provider’s office or pharmacy to get the vaccine.”

It can take up to two weeks for the body to build up defenses against the virus, he added.

The vaccine protect individuals from the flu, but also helps prevent spreading it to the sick, the elderly, pregnant women, and children -- all of whom are more likely to have serious consequences from influenza.

It is especially important for pregnant women to get the vaccine, according to Schaffner.

"There is dual benefit for the pregnant woman to get vaccinated," he said. "Not only will she get protection, but she’ll also pass those antibodies along to her infant, which will protect them for the first 6 months of life when the infant is too young to get the vaccine. And the vaccine is safe for pregnant women and the fetus.”

For those who contract the flu, it could make symptoms less severe, Schaffner added. According to the CDC, the vaccine helps to reduce doctor’s visits, missed school or work and hospitalizations due to the flu.

Other precautions to protect against the flu

Next, make sure to wash hands carefully to limit the spread of the virus and try to avoid close contact with sick people.

For those who do get the flu, Shaffner said, avoid contact with others.

"Stay home, don’t go to work, don’t go to the gym, don’t go to religious services," he said. "Nobody wants to be a dreaded spreader."

And remember to consider antiviral medications, like Tamiflu.

“If you get sick, call your provider, because your provider might prescribe an antiviral,” Schaffner said. “If we get in early enough, we can make your infection less severe, perhaps shorten it by a day and make it less likely that you get the complications.”

People who get sick should also keep up with fluids -- and seek medical attention if they start to feel worse or develop shortness of breath, worsening congestion or cough.