The 2017–18 flu season has been especially severe and deadly, and it’s not over yet.

The flu is raging across the US, with widespread activity in 49 states, and influenza-associated deaths are on the rise.

"It has been a tough flu season so far this year," Dan Jernigan, director of the Influenza Division of the National Center for Immunization and Respiratory Diseases, told reporters in a press briefing Friday. Although flu activity is beginning to go down in parts of the country, such as California, it remains high for most of the US. In fact, 49 states have reported widespread flu activity for three weeks in a row, which is notable.

The predominant strain, H3N2, is not new, but it is known for being particularly nasty. In H3N2 seasons, there are "more cases, more visits to the doctor, more hospitalizations, and more deaths, especially among older people," Jernigan says.

This year's season looks similar to 2014–15, which was categorized as "high severity" and also had H3N2 acting as the predominant strain. However, the number of influenza-related deaths has risen rapidly in the past week, including seven children who died, bringing the total to 37. "We suspect there will be more deaths, similar to what we've seen in past seasons, as data continue to come in," Jernigan said.

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Doctor visits for influenzalike illnesses are at the highest level since the 2009 H1N1 pandemic.

The number of people going to doctor's offices or emergency departments for influenzalike illness (ILI) increased again this week, Jernigan said, rising to 6.6%. This means 6.6% of all people coming into clinics and emergency departments are coming in for the flu, which is far above the national baseline of 2.2%. "This is the highest level of activity recorded since the 2009 H1N1 pandemic, which peaked at 7.7%," Jernigan said.

So, is this the worst flu season since the 2009 swine flu pandemic? The experts say it's still too early to tell, and gauging "severity" takes many different measures and factors into account. "At this point, we don't know what this season is going to look like. In terms of hospitalizations, it's tracking at the same level as 2014–2015 except for the baby boomer age group, but we are seeing the most influenzalike illness activity since 2009."

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Baby boomers, or adults aged 50 to 64, are being hit unusually hard.

The highest hospitalization rates are still among people 65 years and older, which is normal compared to past seasons, including 2014–15. However, the second most–impacted group of people are aged 50 to 64, which is unusual. Experts do not know exactly why baby boomers are being hit especially hard this year, but it could be due to the fact that the strains circulating this year are different from the strains that boomers were exposed to as children.

In the past two seasons, children aged 0 to 4 years have been the second hardest–hit group after those over 65. "Baby boomers have higher rates than their grandchildren right now," Jernigan said. Another unusual characteristic is that 50- to 64-year-olds who are going to the hospital are sick with both H3N2 and H1N1.

For younger age groups, hospitalization rates are looking similar to or lower than recent seasons. So far, the flu has killed 37 children in the US. Last year, it killed a total of 148. Officials expect the number of pediatric deaths to rise as the data continue to come in from around the country.

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However, the season has not reached its peak yet and is nowhere near over.

This flu season started early, with a large number of cases accumulating around the holidays. However, flu activity continued to increase throughout January, peaking earlier than past seasons. "The spike in cases after the winter holidays is highest among children, so it looks like a big part of the later January activity is flu transmission from kids returning to school," Jernigain said.

So far, flu activity has been elevated for 9 consecutive weeks — but the average duration of a flu season for the past five years is around 16 weeks, but some last as long as 20 weeks. So that means we're only about halfway through this flu season, with many more weeks to go. "In 2014–2015, there were an estimated 34 million people who had the flu and 710,000 hospitalizations — this gives a sense about where we might end up this season," Jernigan said.

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The best way to protect yourself is to get a flu shot if you haven't already. It's not too late.

The flu shot is not perfect, but it's your best defense. The CDC is still recommending that anyone over the age of 6 months get a flu shot, because the flu will continue to circulate for several more weeks. Experts will not know how effective the 2017–18 flu vaccine is until this season is over, but current predictions are around 30% for H3N2, BuzzFeed News previously reported. However, the flu shot also protects against H1N1 and influenza B, which have a higher vaccine effectiveness and are also circulating this year.

Even if the flu shot isn't super effective, it's better to have some protection against the circulating strains than no protection at all. The vaccine can also mitigate illness, so if you do get the flu, it will be a less severe, shorter course. In short, the flu shot can keep you out of the hospital.

It's not too late, but you should get it sooner rather than later. Talk to your doctor about whether the flu shot is safe for you and which type you'll need. Use the CDC’s Flu Vaccine Finder to find out which pharmacies and clinics are offering the shot in your area.

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If you think you have the flu, stay home. And go to the doctor if you are considered high risk.

While most people who get the flu will recover within a week, sometimes it can cause more severe illness leading to hospitalization or death. If you are otherwise healthy but have severe flu symptoms — a high and persistent fever, shortness of breath, chest pain, or inner ear pain — go to the doctor. Antivirals like Tamiflu can lessen the severity and shorten the course of the flu, but they're more effective the sooner you take them. Don't wait until you feel really bad, because the flu moves fast.

This is especially important for people who are high risk, such as the elderly, young children, pregnant women, or those with underlying illnesses. These groups are particularly vulnerable and can benefit the most from antivirals. If you are high risk and think you have the flu, go to your doctor or a hospital immediately. Don't wait until you feel really bad, because flu symptoms can quickly get worse.

If you have the flu, stay home and do not go to work or school. You should also wash your hands frequently and cover your mouth if you cough or sneeze.

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