Flu Season: What to Know This Year

Influenza virus

Editor's Note: This story was updated March 27, 2018.

This year's miserable flu season is slowing down.

Flu activity has been decreasing nationwide. And for the first time this season, the CDC reported more cases from the B virus than A for the week ending March 17. Of the two types of viruses that cause flu, the A virus tends to cause more severe illness, and this year's vaccine did not match it as well. 

Still, the season could possibly get a second wind if B viruses -- which hit young children harder -- continue to increase.  Also, it's possible to get infected with a different strain of the flu in the same season. 

Flu is a contagious disease, and it can cause mild to severe symptoms along with life-threatening complications, even in young, healthy children and adults. Adults 65 and over, followed by adults 50-64, and then children from newborn to 4 years old, are those most likely to be hospitalized this season.

Since 2010, the flu has killed from 12,000 to 56,000 people annually in the U.S. and affected about 9 million to 35 million annually.

Here is what else to know about flu.

What's the latest news about this year's flu season?

The CDC says 17 states are experiencing widespread flu activity. The agency says 133 children have died from flu or flu-related complications. It doesn't directly track adult deaths.

How effective is this year's flu vaccine?

The vaccine is only 25 percent effective against more severe H3N2 flu virus, which is causing most cases this year.

Among children aged 6 months through 8 years old, however, the vaccine's effectiveness is 59 percent, the CDC says.

It's also worked better against other types of flu. It's 42 percent effective against the influenza B viruses, which are also circulating, the researchers said. Cases from that type of virus, which generally causes less severe illness, are on the rise.

There are many strains of the two types of flu viruses, A and B, that infect humans. In order to have flu shots ready for flu season, experts have to decide, months in advance, which strains to include in the vaccine. Because strains can change quickly, the vaccine is not always a good match.

Even when the vaccine is a good match, the way it is produced may limit how well it works.

In November, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, along with experts from the World Health Organization and Australia, warned that the way most flu shots are produced in the U.S.—by growing their active ingredients in chicken eggs—may diminish their effectiveness.  Because the vaccine strains have to be changed slightly to allow them to grow in eggs, they may lose their ability to help the body fight the infection. Egg production may be one reason this year’s flu shot was only 10% effective in Australia.

Although the season is waning, public health officials say it's not too late to get a flu shot.

What alternative treatments are people trying?

There has been a lot of Internet discussion about people using elderberry extract and onions -- yes, onions.

Elderberry is getting a lot of buzz, but health experts say the jury is out. This natural remedy may help treat flu and cold symptoms by cutting congestion and perhaps by making you sweat more, experts at the University of Maryland say. In one study, an elderberry extract called Sambucol helped shorten how long the flu lasts by about 3 days. But the product also has other herbs, plus vitamin C, so it's unclear whether the elderberry alone helped.

In another study, a lozenge with elderberry extract helped ease flu symptoms if taken within a day of when the symptoms started. And in the lab, some researchers found elderberry could kill the H1N1 flu virus -- but that was in test tubes, not people. According to the National Center for Complementary and Integrative Health: "Although some preliminary research indicates that elderberry may relieve flu symptoms, the evidence is not strong enough to support its use for this purpose."

And a caution: The raw berries have a chemical similar to cyanide and must be cooked.

As for onions, there are reports of people putting slices of red or white onions on the soles of their feet and then putting on socks to try to cure flu, cold, cough, or fever.

While that remedy has been making the rounds, there's no evidence that it works. Backers say the sulphuric compounds from onions on the feet can enter the body and then kill bacteria and viruses. But medical experts roundly dismiss the idea.

Snopes.com, the website devoted to squashing rumors and myths, gives it a ''False" stamp, adding:  ''Sleeping with onion slices in your socks might give you more space in bed, but it's certainly not fixing anything medically."

On the plus side: You won't hurt anything, except maybe your personal relationships, by trying it.

Where do I get the flu vaccine?

It's offered at doctors' offices, clinics, health departments, college health centers, pharmacies, and at many offices and some schools.

Many insurance plans pay for the annual vaccination, and older adults covered under Medicare Part B can get the vaccine free, with no copay or deductible.

To find a source for vaccines in your area, go to the Vaccine Locator (http://vaccine.healthmap.org).

HealthDay contributed to this report.

How do experts decide what to put into the flu vaccine?

During flu season, experts study samples of the viruses circulating to evaluate how well the vaccine protected against those viruses. They use that information to help make their decision for the next one.

Like all other vaccines, the flu vaccine isn't perfect, but it is up to 60% effective overall in the general population, the CDC says. In general, vaccines work better against influenza B and influenza A (H1N1) viruses than they do again influenza A (H3N2) viruses, the CDC says.

Who gets hit the hardest?

Children, older adults, pregnant women, anyone with a chronic medical condition, and health care workers are especially vulnerable to getting the flu or to have complications such as pneumonia, bronchitis, and sinus and ear infections, the CDC says.

Children younger than 2 are especially vulnerable. Those ages 6 months and under are also much more likely to get complications, but they're too young to be vaccinated, so the best idea is to be sure everyone in contact with them is vaccinated.

Adults ages 65 years and above are at greater risk than younger, healthy adults due to weakened immune systems. Typically, these older adults account for most flu-related deaths and more than half of flu-related hospitalizations.

Pregnant women, as well as those who have delivered a baby in the previous 2 weeks, are more likely to have a severe illness than nonpregnant women.

Anyone with a chronic medical condition is more likely to have complications. These conditions include:

  • Asthma
  • Diabetes
  • Heart disease
  • Obesity
  • A compromised immune system due to cancer, HIV, or other conditions

When does flu season begin and end?

Although you can get the flu anytime, flu season starts in October and can go as late as March and even April. But ''it usually peaks in the U.S. in February, says William Schaffner, MD, medical director of the National Foundation for Infectious DiseasesSchaffner, who's also a professor of preventive medicine at Vanderbilt University School of Medicine, Nashville.

What types of flu shots are available this year?

For the 2017-2018 season, there are several vaccines:

  • Trivalent vaccines, which protect against three flu strains: two A and one B
  • Quadrivalent vaccines, which protect against fours strains: two A and two B
  • A high-dose vaccine that protects against two A and one B strain, meant for adults 65 and above, who usually have weaker immune systems
  • An adjuvanted vaccine, made using an ingredient that helps trigger a stronger immune response, is also an option for older adults. It protects against two A strains and one B.
  • A recombinant vaccine is an egg-free option for people with egg allergies. It protects against two A strains and one B strain.

Children who have never been vaccinated against influenza will need two doses, spaced at least 4 weeks apart.

Is one type of vaccine better than another?

While the quadrivalent vaccine protects against more viruses, the CDC says there is no preference among the recommended and approved vaccines. Ask your doctor which is best for you. Different vaccines are approved for different age groups.

Up to 166 million doses of the flu vaccine are expected to be produced for this flu season, including 119 quadrivalent. However, if it is not available, it is better to get another flu vaccine than to wait for it, the CDC says.

Any flu shot is better than none. Don’t delay getting one if you can't get your first choice.

Who should get a flu shot, and when?

In general, everyone over 6 months of age should get vaccinated -- the earlier the better for getting the vaccine. Late September is a good time, Schaffner says, and even into October and beyond.

Who should not get a flu shot?

Anyone who developed Guillain-Barre syndrome within 6 weeks of a previous flu vaccination should not get vaccinated, the CDC says. Nor should anyone with a known severe, life-threatening allergy to any ingredients in a vaccine.

What about pregnant women? A recent study linked flu vaccine and odds of miscarriage.

In that study, published in the journal Vaccine in September 2017, researchers found a link -- but could not prove cause and effect -- between women who were vaccinated against influenza A H1N1 strains for two consecutive seasons and miscarriage.

However, previous research had not found a higher risk, says Schaffner, who's also a professor of preventive medicine at Vanderbilt University School of Medicine, Nashville. The researchers are continuing to study the issue, and some experts wonder if the finding might be a statistical fluke, he says.

The CDC continues to recommend vaccination for pregnant women.

Pregnant women who get vaccinated also lower the risk of flu in their baby, Schaffner says. "Some of that protection goes across the placenta and protects the baby for the first 6 months" before immunization is recommended, he says.

How long does it take for the flu shot to become effective?

It takes about 10 days to 2 weeks for the vaccine to reach its top strength, says Schaffner.

What about the nasal spray flu vaccine?

The nasal spray vaccine, FluMist, is not recommended by the CDC because it doesn’t work well.

I hate needles. What can I do?

Even some health care providers have needle phobia, says Patricia Stinchfield, RN, senior director of infection prevention and control and a pediatric nurse practitioner at Children's Minnesota.

The strategy she suggests to help children through the injection can also work for needle-wary adults, she says. "Close your eyes. Breathe through your mouth. Relax your arm. Imagine your favorite place. Before you know it, it will be over."

What are common symptoms of the flu?

They usually come more suddenly than cold symptoms. They include fever, feeling feverish, the chills, having a cough, sore throat, runny nose, muscle or body aches, headache, and fatigue. Less common are vomiting and diarrhea. Children are more likely to have vomiting and diarrhea than adults are, the CDC says.

Not everyone with the flu has a fever.

What should I do I if I think I am getting the flu?

Stay home, rest, and avoid contact with others except to get medical care if needed, experts say. Avoid contact with others for at least 24 hours after the fever subsides to avoid spreading the flu.

Be on the lookout for emergency warning signs that you may be developing serious flu-related complications, the CDC advises.

In children, these include:

  • Fast or troubled breathing
  • Bluish skin color
  • Severe irritability
  • Fever plus a rash
  • Lack of interaction
  • Not drinking fluids
  • Symptoms that improve then return with fever and a worse cough

In adults, they include:

  • Breathing trouble
  • Pain or pressure in the chest or abdomen
  • Dizziness or confusion
  • Severe or persistent vomiting

Symptoms that improve but then return with a fever and worsening cough.

What are the treatments for the flu?

The FDA has approved three antivirals for flu, including oseltamivir (generic or Tamiflu), peramivir (Rapivab), and zanamivir (Relenza).

Antiviral drugs can lessen your symptoms and shorten sick time by 1 or 2 days, according to the CDC. These are prescription medicines in various forms, such as pills, liquid, an inhaled powder, or an IV solution. Ask your doctor if they are right for you.

It's important to start the drugs early, as studies show they work best when started within 2 days of getting sick. However, your doctor may decide they can still be helpful if started later than that.

Besides getting vaccinated, what else can help lower the chance of getting the of flu?

Everyday preventive actions ae important. Avoid people who are ill, and practice good hygiene such as washing your hands often and covering your cough. If you are sick, stay home.

WebMD Article Reviewed by Neha Pathak, MD on October 18, 2017


CDC: "Key Facts About Seasonal Flu Vaccine," "Vaccination: Who Should Do It, Who Should Not and Who Should Take Precautions," "Flu Symptoms & Complications," "What You Should Know About Flu Antiviral Drugs," "How Effective Is the Flu Vaccine?" "Pregnant Women and Influenza (Flu)."

William Schaffner, MD, medical director, National Foundation for Infectious Diseases; professor of preventive medicine, Vanderbilt University School of Medicine, Nashville.

National Foundation for Infectious Diseases news conference, Sept. 28, 2017.

Patricia Stinchfield, RN, senior director, infection prevention and control, and pediatric nurse practitioner, Children's Minnesota.

New England Journal of Medicine, "Chasing Seasonal Influenza — The Need for a Universal Influenza Vaccine."

 Nicole Capone, public information officer, Arizona Department of Health Services.


Fox News, “Mom of 2 dies day after flu diagnosis.”

Kristen Nordlund, spokesperson, CDC.

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Denver Post, “Flu has sent more than three times the number of people to the hospital in Colorado than usual.”

CNN, "Parents of young children have reason to be watchful as flu season ends."

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