So why is this current flu season so deadly—and what can you still to do to protect yourself while you wait it out? In fact, why is there such a thing as “flu season” at all? Here’s what you need to know.

How many people die from the flu?

The 2018 flu season is getting attention, and for good reason. It’s a particularly vicious one dominated by the H3N2 flu strain, which is especially dangerous for elder Americans. In San Diego, California, 34 people died from the flu in the last week of 2017 alone. And that’s been the story across the country at large, too.

“While most Americans were traveling and visiting family between Dec. 24 and Dec. 30, 2017, data from athenaInsight’s 2017 – 2018 Flu Dashboard showed that 4.34 percent of more than 1 million outpatient visits across the country were coded for influenza-like illness (ILI),” according to athenahealth analytics arm athenaInsight. To put that in perspective: At the same time last year, just 2.07% of these visits were coded for influenza-like illness, or less than half of what physicians have seen in 2018.

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So why are so many people dying from the flu (or going to the hospital because of it) this year? For one, the most recent flu vaccine may only wind up being 30% to 40% effective, versus a typical range of 40% to 60% efficacy. And this year’s dominant strain, H3N2, is widely considered a nasty one.

It will take at least two to three more months to assess most of the damage from this year’s flu season. (Public health experts believe it’s peaking right about now, but millions of other Americans will likely catch the flu at some point over the next ten or so weeks, especially as other strains like H1N1 rise.) But, it’s also important to note that anywhere from 5% to 20% of the population gets the flu in any given year, hundreds of thousands are hospitalized, and tens of thousands die—which is why health officials always urge everyone who’s medically capable to get a flu vaccine, even if it’s less effective in a given year.

Why does the flu have a “season”?

There’s a simple reason why we are supposed to get our flu shots in the fall: The influenza virus happens to thrive most just afterward, peaking between December and February (aka right about now), and it takes about two weeks for the flu vaccine to kick in. Earlier protection is better since the length of flu season can technically last from October through May.

But cold weather and the holiday season are two potential reasons flu seems to dominate during mid-winter (though there’s some debate about the root cause). For one, the virus may be able to thrive more in dry, wintry conditions than it would in the dog days of summer (low humidity may also make it easier for the flu to attack the lungs). And the holiday travel boom allows many different strains of flu to cross the country.

How can I still protect myself from the flu?

The most important way you can protect yourself—and others, especially older people, children, and those with compromised immune systems—from the flu is to get a flu shot. You can still get them at many retail clinics for free or close-to-free. Here’s a roundup of where you can get the flu vaccine (and for how much).

It’s also important to take common sense measures to stop the spread of germs, as the CDC outlines here. Stay away from sick people (and do not go into work if you’re sick, if it’s at all avoidable). And make sure to wash your hands with soap and water regularly. There’s no need to spring for antibacterial soaps, though; the flu is a virus so it won’t do any good (and could just lend to more antibiotic resistant bacteria).

If you do get sick with flu, go to the doctor, take any anti-viral medications that he or she prescribes, and get plenty of rest and fluids.