What doctors wish patients knew about the flu

With the COVID-19 pandemic and all its precautions—masking, physical distancing and staying home—influenza activity was drastically lower in 2020 and 2021 than in previous years.

Now the flu is back, with hospitalizations at their highest levels and case counts continuing to rise across the country. Yet with a “tripledemic” of COVID-19, respiratory syncytial virus (RSV) and influenza, it may be hard to know which virus you have. An infectious diseases physician sets out to clear things up about influenza to navigate the flu season.

This season, there have been at least 22 million flu illnesses and 8.6–18 million influenza medical visits. There have also been about 230,000 hospitalizations due to the flu and 14,000 influenza deaths, according to estimates from the Centers for Disease Control and Prevention.

The AMA’s What Doctors Wish Patients Knew™ series gives physicians a platform to share what they want patients to understand about today’s health care headlines.

In this installment, Preeti Malani, MD, an infectious diseases physician and professor of medicine in the infectious diseases division at the University of Michigan Medical School, took time to discuss what patients need to know about influenza. Dr. Malani is also deputy editor of JAMA^®.

The “flu is a respiratory illness caused by the influenza virus. And there are two types of flu—there's type influenza A and influenza B,” Dr. Malani said. “Those are important because the way the vaccine works is it includes particular types of the flu.”

Influenza A and B viruses cause seasonal epidemics—known as flu season—that happen almost every winter in the U.S., she noted. And the influenza A virus is the only type known to cause flu pandemics, such as H1N1 in 2009.

“Influenza A viruses are divided into subtypes based on two proteins on the surface of the virus, which are hemagglutinin and neuraminidase,” Dr. Malani explained, noting that this helps in “understanding where the flu came from and what its genetics look like. It also determines treatment options.”

For example, “influenza B is less common, but we may want to use a particular drug if someone has flu B,” she said, noting that influenza “A is more prominent than B.” 

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“Normally, we don’t wear masks. This has been something in the last couple years—at least in the United States—so there’s a lot of speculation on why there’s an early rise in flu cases,” Dr. Malani said. “And to be clear, this is the most severe flu season that’s been seen in years and probably the most hospitalizations ever recorded, particularly for November and December.”

“If you look back at 2020, there was no flu because people were in their homes, they were wearing masks if they left their homes, and the COVID-19 vaccines were just becoming available in late December 2020 and those were for the highest risk people,” she said. “Then last year there was a lot of concern that we were going to see this twindemic and although there were some cases of flu, we didn’t see a large wave.”

“So, it’s been three years since there’ve been large numbers of flu cases. And if you go back further to 2009, 2010 with H1N1, that was a very bad couple years. And this year appears to be like that,” Dr. Malani said. “There’s a lot of theory on why and it may just be that we haven’t had flu in a couple years, much like the RSV that we have seen because kids who are 3 years old haven’t had any illness, so they have very little immunity to some of these circulating viruses.”

“Symptoms are usually going to occur within a couple days of exposure, although it could be a little bit longer,” Dr. Malani said. “But this isn’t something that a week later you’re developing symptoms.”

“Something about COVID that surprised me initially was how long that incubation period could be and that’s in part what has helped COVID spread,” she said. “Again, the most current Omicron variants, the incubation period tends to be less long, often within three days, but with flu the average is probably a couple days, maybe up to four.”

“With the flu, it could be fevers, it could be fatigue initially and just feeling like you just don’t feel well. And it could come on pretty suddenly where you’re feeling OK and then you’re just exhausted,” Dr. Malani said, noting that “your body aches and then you can develop the respiratory symptoms later.”

Additionally, “you may have a little cough, congestion and, in someone who’s older or more vulnerable, it could be much more severe. It could become pneumonia,” she said. “And little kids get flu a lot too and they may get fevers and runny noses. That could be how flu presents in someone who’s younger.”

While “it varies from person to person, little kids might get better quicker,” Dr. Malani said. “But most people within a week are going to feel close to baseline.”

However, “four or five days is probably the average, but people might be coughing for weeks,” she said, noting that is because of “inflammation and they may just not feel well for quite a while.”

“COVID-19 testing at home remains very important and very helpful,” said Dr. Malani. “But just because your test is negative doesn’t mean you can go about your business as usual, especially if you have symptoms.”

After ruling out COVID-19, it could still be the flu. But “if you’re not feeling that poorly and you have mild symptoms, it’s fine to stay home. You generally don’t need to go and seek care if you’re otherwise healthy,” she said. “For someone who has more health conditions, is older or pregnant, then getting tested for the flu in your doctor’s office is helpful to determine a proper treatment plan.”

“Right now, there’s just a lot of flu everywhere in the U.S. And one of the things that’s important with flu is that if you do have influenza—not another respiratory virus—there are treatments, but they need to be given early to be most effective,” Dr. Malani said, noting “there are a few different treatment options for the flu.”

“There’s antiviral treatment. So, the main one is oseltamivir, or Tamiflu,” she said. “But there’s a shortage of this drug, so people are being asked to be more thoughtful about who gets prescribed this.”

Then “there is another drug that’s called Baloxavir and this is a one-time dose. It’s also an oral medication and is usually given over five days,” Dr. Malani said.

When it comes to influenza treatment “we think of older adults, little babies, kids under 2 and individuals with chronic illness such as heart disease, lung disease, diabetes, cancer, and anyone with a weakened immune system,” said Dr. Malani. “But pregnancy is also a big one with influenza and this is why during prenatal care, flu shots are really a priority.”

“With flu and pregnancy, those are younger people who we see that end up hospitalized,” she said, emphasizing that “not everyone, but the young people we see who do very poorly with flu are often pregnant.”

“If someone is ill and they have cold symptoms and a cough or fever, it’s really important that they not go out and expose other people,” said Dr. Malani. “And hopefully that’s something that we have socialized. Something that many of us—myself included—have done in the past is we’ve gone to places sick.

“We’ve gone to work sick. We’ve sent our kids to school sick. And the pandemic has really helped socialize the idea that you shouldn’t be going to a social event if you’re not feeling well,” she added. “The system should allow flexibility for work or school or wherever you’re going.”

“Masks are very effective at preventing transmission of respiratory viruses,” Dr. Malani said, and that includes the flu. If someone in your household is sick—like if you have young kids at home—you can’t really isolate because you have to take care of them.

“If you’re able to wear a mask at home, if might help you not get sick. Around the world masks have been used successfully during respiratory virus season,” she said. “And I understand that in the United States a lot of people have moved on and they don’t want to wear masks anymore, but I would strongly encourage people—especially while traveling—to wear a mask in crowded spaces.”

“If you do have the flu, it is important to stay hydrated. You can also take medications to decrease fevers and drink tea or broth,” Dr. Malani said. “But you do want to avoid Aspirin, especially in kids and teens.”

“Acetaminophen or ibuprofen will help with fever. It will also help with muscle aches,” she said, emphasizing that it is important to rest as much as possible when you have the flu.

When it comes to influenza, “the things that are going to be important are prevention,” said Dr. Malani. That means “getting a flu shot” and knowing that “it’s not too late to get a flu shot.”

“The vaccine effectiveness—how well the vaccine is working in the real world—appears to be pretty good for this year,” she said. “And I’ve seen estimates around 50%, which for a flu vaccine is outstanding.”

“While it doesn’t prevent all illness, vaccination prevents severe illness. So, much like COVID-19 vaccines, getting a flu shot will help prevent you from being hospitalized, certainly from death and other severe complications of flu,” Dr. Malani explained. Unfortunately, though, “the numbers are below an optimal uptake and there are a lot of younger people who haven’t been vaccinated. There are actually quite a few older people who haven’t been vaccinated either.”

It may be too late for an influenza vaccine “when there’s not flu circulating anymore, which would probably be in the spring,” she said. “But right now, it’s still a good time to get the flu vaccine and you can get it at the same time as your COVID-19 bivalent booster.”

“This year is on track to being one of the worst flu years in memory. It’s already headed that way, so the more we can do to get the word out to people to remind them to get flu shots, the better we’ll fare,” Dr. Malani emphasized.