Tero Vesalainen / iStock / Getty Images
By Julia Ries
- Two flu strains are overlapping each other this flu season.
- This means you can get sick twice from different flu strains.
- While the flu vaccine isn't a perfect match, it's the best defense against the flu.
To say this flu season has been abnormal is an understatement.
<p>For one, the flu season got its earliest start in 16 years.</p><p>Up to 18 million people have gotten the flu this year, according to the <a href="https://www.cdc.gov/flu/about/burden/preliminary-in-season-estimates.htm" target="_blank">Centers for Disease Control and Prevention's (CDC) latest estimates</a>. Up to 210,000 people have been hospitalized and thousands have died, including <a href="https://www.cdc.gov/flu/weekly/#S3" target="_blank">39 children</a>.</p><p>We're also seeing B strains of the flu dominate, something that hasn't happened in the United States in nearly 30 years.</p><p>And, unfortunately, the vaccine missed the mark with B/Victoria, the most common strain we're seeing this year. The CDC believes the shot only covers about <a href="https://www.healthline.com/health-news/flu-season-2020-what-to-know#The-vaccine-isnt-perfect,-but-it-helps" target="_blank">58 percent</a> of B-linked cases.</p><p>Now, halfway through flu season, A strains are picking up, increasing the odds we'll have a "double-barreled flu season," in which two strains strike back to back — a pattern health experts say is extremely rare.</p><p>Between the early start, rise in B strains, and recent spike in A-strain illnesses, this flu season officially has infectious disease experts stumped.</p><p>"This season has turned a lot of [what we know about flu] on its head," said <a href="https://www.vumc.org/health-policy/person/william-schaffner-md" target="_blank">Dr. William Schaffner</a>, an infectious disease specialist with Vanderbilt University Medical Center and the medical director at the National Foundation for Infectious Diseases. "There's a lot we know, and even more we don't know about flu."</p>
<p> <em>Reposted with permission from </em><a href="https://www.healthline.com/" target="_blank"><em>Healthline</em></a><em>. For detailed source information, please view the original article on </em><em><a href="https://www.healthline.com/health-news/get-the-flu-twice-this-year" target="_blank">Healthline</a></em><em>.</em><br><em></em></p>
Double-Barreled Flu Season
<p>A double-barreled flu season occurs when two flu outbreaks overlap one another, a pattern which is very unusual, according to flu experts.</p><p>Last year, for example, we saw A/H1N1 infections peak early, followed by another wave of A/H3N2 infections.</p><p>Though the predominant strains are different this year, we're seeing the same pattern play out: Activity took off with B/Victoria and now that second wave of A/H1N1 is coming for us, according to Schaffner.</p><p>"Around the country, my colleagues and I are seeing H1N1 come up strong, and it's now about 50-50 [with B/Victoria]," Schaffner told Healthline.</p><p>The most worrisome part of a double-barreled flu season is that you can get sick twice.</p><p>Just because you caught a B-strain flu doesn't mean that you're immune from the A strains.</p><p>"There will be the rare person who gets two flu infections in the same season — one with B and one with H1N1," Schaffner said.</p><p>Though there will be some protection within each strain — in that contracting an A strain will protect you against other A strains, and B strains will protect against other B's — there's not much cross protection.</p><p>A double-barreled season also means we're more likely to see a prolonged influenza season.</p>What to Know About B and A Strains
<p>The fact that B strains are predominating this year isn't just confusing, it's concerning as well.</p><p>B strains haven't hit this hard for nearly 30 years, since during the 1992–1993 season, the CDC told Healthline.</p><p>Additionally, we didn't see much of the B strain in the past couple of years, according to <a href="http://www.linkedin.com/in/norman-moore-908577a/" target="_blank">Dr. Norman Moore</a>, the director of infectious diseases for <a href="https://www.abbott.com/corpnewsroom/healthy-communities/your-kids-got-the-flu.html" target="_blank">Abbott</a>.</p><p>This means that many people — especially kids — have never been exposed to the strain, and consequently, don't have residual immunity against it.</p><p>"When there's a rarity, it actually sets you up for another bigger push to get it, because at that point, we really don't have anybody with any strong immunity going around, so we're all potential vessels for getting exposed and transmitting it," Moore said.</p><p>This is one of the reasons kids are being hit harder this year. They've never been exposed to this type of the flu — it's their first go around.</p><p>"These kids are just brand new to getting flu B," Moore said.</p><p>And because we haven't seen much of the B/Victoria strain in the past few years, this year's vaccine missed the mark.</p><p>"We thought initially the match was perfect, but it's not. It's off a little bit, and that means in many populations the vaccine is not going to function optimally," Schaffner explained.</p><p>Fortunately, the vaccine covers H1N1 well. According to Schaffner, the match to H1N1 is right on.</p><p>And because A strains circulate every year, most people have built up at least some "immune memory" to it — despite the fact these strains change and mutate each year.</p><p>"Our past experience with influenza viruses does give us some residual protection that lasts," Schaffner said.</p>There’s Still Time to Get Vaccinated
<p>"It's not too late," Moore said about the vaccine, noting that we still don't know for sure what's going to happen next.</p><p>If flu A continues to get worse, as predicted, the flu shot will protect you through the rest of the season.</p><p>And even though the vaccine isn't a perfect match to B strains, it can still help lessen the severity of the flu.</p><p>"If you've been vaccinated, and even if there is a mismatch, you are likely to have a less severe infection when you get it," Schaffner said.</p><p>Remember: By getting immunized, you're not only protecting yourself, but others as well who may be more at risk for developing severe complications — like the elderly, pregnant women, children under 2, and immunosuppressed people.</p><p>"When we protect ourselves, we are really protecting those around us," Moore said.</p>The Bottom Line
<p>Health experts say this has been an extremely unusual flu season. It started very early with a strain that we typically don't see much of. Now, another strain is building momentum and creating a path for what's known as a double-barreled flu season, in which two types of flu strike back to back. With a second wave coming, flu experts say it's not too late to get vaccinated before things pick up again.</p>From Your Site Articles
- 9 Dishes Chefs Eat When They're Sick - EcoWatch ›
- Flu Now Widespread in 45 States, What to Know - EcoWatch ›
- What the Flu Does to Your Body, and Why It Makes You Feel So Awful ›
Related Articles Around the Web
Read More
Show Less
What the Flu Does to Your Body, and Why It Makes You Feel So Awful
12 February 2018
Health + Wellness
By Laura Haynes
Every year, from 5 to 20 percent of the people in the U.S. will become infected with the influenza virus. An average of 200,000 of these people will require hospitalization and up to 50,000 will die. Older folks over the age of 65 are especially susceptible to influenza infection, since the immune system becomes weaker with age. In addition, older folks are also more susceptible to long-term disability following influenza infection, especially if they are hospitalized.
<p>
We all know the <a href="https://www.cdc.gov/flu/consumer/symptoms.htm" target="_blank">symptoms of influenza</a> infection include fever, cough, sore throat, muscle aches, headaches and fatigue. But just what causes all the havoc? What is going on in your body as you fight the flu?
</p><p>
I am a researcher who specializes in immunology at the University of Connecticut School of Medicine, and my laboratory focuses on how influenza infection affects the body and how our bodies combat the virus. It's interesting to note that many of the body's defenses that attack the virus also cause many of the symptoms associated with the flu.
</p><p><strong>How the Flu Works Its Way Into Your Body</strong></p><p>
Influenza virus causes an infection in the <a href="https://www.cdc.gov/flu/keyfacts.htm" target="_blank">respiratory tract</a>, or nose, throat and lungs. The virus is inhaled or transmitted, usually via your fingers, to the mucous membranes of the mouth, nose or eyes. It then travels down the respiratory tract and binds to epithelial cells lining the lung airways via specific molecules on the cell surface. Once inside the cells, the virus hijacks the protein manufacturing machinery of the cell to generate its own viral proteins and create more viral particles. Once mature viral particles are produced, they are released from the cell and can then go on to invade adjacent cells.</p><p class="shortcode-media shortcode-media-rebelmouse-image">
<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xNzE5NjgyNy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNzA5OTM4M30.EYnF5QHuO8tSRTvucO4AEe5qWlJp-LguU2UbQi4_xOc/img.jpg?width=980" id="b2f70" class="rm-shortcode" data-rm-shortcode-id="70c676c5018f4027f26e11f23f989ab0" data-rm-shortcode-name="rebelmouse-image">
<small class="image-media media-caption" placeholder="add caption...">Influenza gets a foothold in the respiratory tract but can make a person feel bad all over. </small><small class="image-media media-photo-credit" placeholder="add photo credit...">Africa Studio / Shutterstock.com</small></p><p>While this process causes some lung injury, most of the symptoms of the flu are actually caused by the immune response to the virus. The initial immune response involves cells of the body's innate immune system, such as <a href="https://www.hindawi.com/journals/mi/2016/5894347/" target="_blank">macrophages and neutrophils</a>. These cells express receptors that are able to sense the presence of the virus. They then sound the alarm by producing small hormone-like molecules called <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785020/" target="_blank">cytokines</a> and <a href="https://www.news-medical.net/health/What-are-Chemokines.aspx" target="_blank">chemokines</a>. These alert the body that an infection has been established.<br></p><p>
Cytokines orchestrate other components of the immune system to appropriately fight the invading virus, while chemokines direct these components to the location of infection. One of the types of cells called into action are <a href="https://www.medicinenet.com/script/main/art.asp?articlekey=11300" target="_blank">T lymphocytes</a>, a type of white blood cell that fights infection. Sometimes, they are even called "soldier" cells. When T cells specifically recognize influenza virus proteins, they then begin to proliferate in the lymph nodes around the lungs and throat. This causes swelling and pain in these lymph nodes.
</p><p>
After a few days, these T cells move to the lungs and begin to kill the virus-infected cells. This process creates a great deal of lung damage similar to bronchitis, which can worsen existing lung disease and make breathing difficult. In addition, the buildup of mucous in the lungs, as a result of this immune response to infection, induces <a href="https://www.medicalnewstoday.com/articles/320190.php" target="_blank">coughing as a reflex</a> to try to clear the airways. Normally, this damage triggered by arrival of T cells in the lungs is reversible in a healthy person, but when it advances, it is bad news and can lead to death.
</p><p>
The proper functioning of influenza-specific T cells is critical for efficient clearance of the virus from the lungs. When T cell function declines, such as with increasing age or during use of immunosuppressive drugs, viral clearance is delayed. This results in a prolonged infection and greater lung damage. This can also set the stage for complications including secondary <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5481322/#B24" target="_blank">bacterial pneumonia</a>, which can often be deadly.
</p><p><strong>Why Your Head Hurts So Much</strong></p><p>
While the influenza virus is wholly contained in the lungs under normal circumstances, several symptoms of influenza are systemic, including fever, headache, fatigue and <a href="https://www.cdc.gov/flu/consumer/symptoms.htm" target="_blank">muscle aches</a>. In order to properly combat influenza infection, the cytokines and chemokines produced by the innate immune cells in the lungs become systemic—that is, they enter the bloodstream, and contribute to these systemic symptoms. When this happens, a cascade of complicating biological events occur.
</p><p>
One of the things that happens is that <a href="https://www.ncbi.nlm.nih.gov/pubmed/9620641" target="_blank">Interleukin-1</a>, an inflammatory type of cytokine, is activated. Interleukin-1 is important for developing the killer T cell response against the virus, but it also affects the part of the brain in the hypothalamus that regulates body temperature, resulting in fever and headaches.
</p><p>
Another important cytokine that fights influenza infection is something called "<a href="https://www.webmd.com/rheumatoid-arthritis/how-does-tnf-cause-inflammation#1" target="_blank">tumor necrosis factor alpha</a>." This cytokine can have<a href="http://jvi.asm.org/content/76/3/1071.full" target="_blank"> direct antiviral effects</a> in the lungs, and that's good. But it can also cause fever and appetite loss, fatigue and weakness during influenza and other types of infection.
</p><p><strong>Why Your Muscles Ache</strong></p><p>
Our research has also uncovered another aspect of <a href="http://www.aging-us.com/article/100882/text" target="_blank">how influenza infection affects our bodies</a>.
</p><p>
It is well-known that muscle aches and weakness are prominent symptoms of influenza infection. Our study in an animal model found that influenza infection leads to an increase in the expression of muscle-degrading genes and a decrease in expression of muscle-building genes in skeletal muscles in the legs.
</p><p>
Functionally, influenza infection also hinders walking and leg strength. Importantly, in young individuals, these effects are transient and return to normal once the infection was cleared.
</p><p>
In contrast, these effects can linger significantly longer in older individuals. This is important, since a decrease in leg stability and strength could result in older folks being more prone to falls during recovery from influenza infection. It could also result in long-term disability and lead to the need for a cane or walker, limiting mobility and independence.
</p><p>
Researchers in my lab think that this impact of influenza infection on muscles is another unintended consequence of the immune response to the virus. We are currently working to determine what specific factors produced during the immune response are responsible for this and if we can find a way to prevent it.
</p><p>
Thus, while you feel miserable when you have an influenza infection, you can rest assured that it is because your body is fighting hard. It's combating the spread of the virus in your lungs and killing infected cells.
</p><p>
<em>Reposted with permission from our media associate <a href="https://theconversation.com/what-the-flu-does-to-your-body-and-why-it-makes-you-feel-so-awful-91530" target="_blank">The Conversation</a>.</em>
</p><script async="async" data-counter="https://counter.theconversation.com/content/91530/count?distributor=republish-lightbox-advanced" id="theconversation_tracker_hook" src="https://theconversation.com/javascripts/lib/content_tracker_hook.js" type="text/javascript"></script>
Related Articles Around the Web
Read More
Show Less