Sorry, You Might Get the Flu Twice This Year — Here’s Why
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.
For one, the flu season got its earliest start in 16 years.
Up to 18 million people have gotten the flu this year, according to the Centers for Disease Control and Prevention's (CDC) latest estimates. Up to 210,000 people have been hospitalized and thousands have died, including 39 children.
We're also seeing B strains of the flu dominate, something that hasn't happened in the United States in nearly 30 years.
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 58 percent of B-linked cases.
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.
Between the early start, rise in B strains, and recent spike in A-strain illnesses, this flu season officially has infectious disease experts stumped.
"This season has turned a lot of [what we know about flu] on its head," said Dr. William Schaffner, 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."
Double-Barreled Flu Season
A double-barreled flu season occurs when two flu outbreaks overlap one another, a pattern which is very unusual, according to flu experts.
Last year, for example, we saw A/H1N1 infections peak early, followed by another wave of A/H3N2 infections.
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.
"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.
The most worrisome part of a double-barreled flu season is that you can get sick twice.
Just because you caught a B-strain flu doesn't mean that you're immune from the A strains.
"There will be the rare person who gets two flu infections in the same season — one with B and one with H1N1," Schaffner said.
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.
A double-barreled season also means we're more likely to see a prolonged influenza season.
What to Know About B and A Strains
The fact that B strains are predominating this year isn't just confusing, it's concerning as well.
B strains haven't hit this hard for nearly 30 years, since during the 1992–1993 season, the CDC told Healthline.
This means that many people — especially kids — have never been exposed to the strain, and consequently, don't have residual immunity against it.
"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.
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.
"These kids are just brand new to getting flu B," Moore said.
And because we haven't seen much of the B/Victoria strain in the past few years, this year's vaccine missed the mark.
"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.
Fortunately, the vaccine covers H1N1 well. According to Schaffner, the match to H1N1 is right on.
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.
"Our past experience with influenza viruses does give us some residual protection that lasts," Schaffner said.
There’s Still Time to Get Vaccinated
"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.
If flu A continues to get worse, as predicted, the flu shot will protect you through the rest of the season.
And even though the vaccine isn't a perfect match to B strains, it can still help lessen the severity of the flu.
"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.
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.
"When we protect ourselves, we are really protecting those around us," Moore said.
The Bottom Line
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.
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By Bob Jacobs
Hanako, a female Asian elephant, lived in a tiny concrete enclosure at Japan's Inokashira Park Zoo for more than 60 years, often in chains, with no stimulation. In the wild, elephants live in herds, with close family ties. Hanako was solitary for the last decade of her life.
Hanako, an Asian elephant kept at Japan's Inokashira Park Zoo; and Kiska, an orca that lives at Marineland Canada. One image depicts Kiska's damaged teeth. Elephants in Japan (left image), Ontario Captive Animal Watch (right image), CC BY-ND
Affecting Health and Altering Behavior<p>It is easy to observe the overall health and psychological consequences of life in captivity for these animals. Many captive elephants suffer from arthritis, obesity or skin problems. Both <a href="https://doi.org/10.11609/JoTT.o2620.1826-36" target="_blank">elephants</a> and orcas often have severe dental problems. Captive orcas are plagued by <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank">pneumonia, kidney disease, gastrointestinal illnesses and infections</a>.</p><p>Many animals <a href="https://doi.org/10.1016/j.neubiorev.2017.09.010" target="_blank">try to cope</a> with captivity by adopting abnormal behaviors. Some develop "<a href="https://doi.org/10.1016/j.applanim.2017.05.003" target="_blank" rel="noopener noreferrer">stereotypies</a>," which are repetitive, purposeless habits such as constantly bobbing their heads, swaying incessantly or chewing on the bars of their cages. Others, especially big cats, pace their enclosures. Elephants rub or break their tusks.</p>
Changing Brain Structure<p>Neuroscientific research indicates that living in an impoverished, stressful captive environment <a href="https://doi.org/10.1016/j.jveb.2019.05.005" target="_blank" rel="noopener noreferrer">physically damages the brain</a>. These changes have been documented in many <a href="https://doi.org/10.1002/cne.903270108" target="_blank" rel="noopener noreferrer">species</a>, including rodents, rabbits, cats and <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">humans</a>.</p><p>Although researchers have directly studied some animal brains, most of what we know comes from observing animal behavior, analyzing stress hormone levels in the blood and applying knowledge gained from a half-century of neuroscience research. Laboratory research also suggests that mammals in a zoo or aquarium have compromised brain function.</p>
This illustration shows differences in the brain's cerebral cortex in animals held in impoverished (captive) and enriched (natural) environments. Impoverishment results in thinning of the cortex, a decreased blood supply, less support for neurons and decreased connectivity among neurons. Arnold B. Scheibel, CC BY-ND<p>Subsisting in confined, barren quarters that lack intellectual stimulation or appropriate social contact seems to <a href="https://doi.org/10.1590/S0001-37652001000200006" target="_blank" rel="noopener noreferrer">thin the cerebral cortex</a> – the part of the brain involved in voluntary movement and higher cognitive function, including memory, planning and decision-making.</p><p>There are other consequences. Capillaries shrink, depriving the brain of the oxygen-rich blood it needs to survive. Neurons become smaller, and their dendrites – the branches that form connections with other neurons – become less complex, impairing communication within the brain. As a result, the cortical neurons in captive animals <a href="https://doi.org/10.1002/cne.901230110" target="_blank">process information less efficiently</a> than those living in <a href="https://doi.org/10.1002/dev.420020208" target="_blank">enriched, more natural environments</a>.</p>
An actual cortical neuron in a wild African elephant living in its natural habitat compared with a hypothesized cortical neuron from a captive elephant. Bob Jacobs, CC BY-ND<p>Brain health is also affected by living in small quarters that <a href="https://doi.org/10.3233/BPL-160040" target="_blank">don't allow for needed exercise</a>. Physical activity increases the flow of blood to the brain, which requires large amounts of oxygen. Exercise increases the production of new connections and <a href="http://dx.doi.org/10.1126/science.aaw2622" target="_blank">enhances cognitive abilities</a>.</p><p>In their native habits these animals must move to survive, covering great distances to forage or find a mate. Elephants typically travel anywhere from <a href="https://www.elephantsforafrica.org/elephant-facts/#:%7E:text=How%20far%20do%20elephants%20walk,km%20on%20a%20daily%20basis." target="_blank">15 to 120 miles per day</a>. In a zoo, they average <a href="https://doi.org/10.1371/journal.pone.0150331" target="_blank" rel="noopener noreferrer">three miles daily</a>, often walking back and forth in small enclosures. One free orca studied in Canada swam <a href="https://doi.org/10.1007/s00300-010-0958-x" target="_blank" rel="noopener noreferrer">up to 156 miles a day</a>; meanwhile, an average orca tank is about 10,000 times smaller than its <a href="https://www.cascadiaresearch.org/projects/killer-whales/using-dtags-study-acoustics-and-behavior-southern" target="_blank" rel="noopener noreferrer">natural home range</a>.</p>
Disrupting Brain Chemistry and Killing Cells<p>Living in enclosures that restrict or prevent normal behavior creates chronic frustration and boredom. In the wild, an animal's stress-response system helps it escape from danger. But captivity traps animals with <a href="https://doi.org/10.1073/pnas.1215502109" target="_blank">almost no control</a> over their environment.</p><p>These situations foster <a href="https://doi.org/10.1037/rev0000033" target="_blank">learned helplessness</a>, negatively impacting the <a href="https://doi.org/10.1155/2016/6391686" target="_blank" rel="noopener noreferrer">hippocampus</a>, which handles memory functions, and the <a href="https://doi.org/10.1016/j.neuropharm.2011.02.024" target="_blank" rel="noopener noreferrer">amygdala</a>, which processes emotions. Prolonged stress <a href="https://doi.org/10.3109/10253899609001092" target="_blank" rel="noopener noreferrer">elevates stress hormones</a> and <a href="https://doi.org/10.1523/JNEUROSCI.10-09-02897.1990" target="_blank" rel="noopener noreferrer">damages or even kills neurons</a> in both brain regions. It also disrupts the <a href="https://doi.org/10.1016/j.neubiorev.2005.03.021" target="_blank" rel="noopener noreferrer">delicate balance of serotonin</a>, a neurotransmitter that stabilizes mood, among other functions.</p><p>In humans, <a href="https://doi.org/10.1006/nimg.2001.0917" target="_blank" rel="noopener noreferrer">deprivation</a> can trigger <a href="https://doi.org/10.3389/fnins.2018.00367" target="_blank" rel="noopener noreferrer">psychiatric issues</a>, including depression, anxiety, <a href="https://doi.org/10.3389/fnins.2018.00367" target="_blank" rel="noopener noreferrer">mood disorders</a> or <a href="https://doi.org/10.1177/1073858409333072" target="_blank" rel="noopener noreferrer">post-traumatic stress disorder</a>. <a href="https://doi.org/10.1007/s00429-010-0288-3" target="_blank" rel="noopener noreferrer">Elephants</a>, <a href="https://doi.org/10.1371/journal.pbio.0050139" target="_blank" rel="noopener noreferrer">orcas</a> and other animals with large brains are likely to react in similar ways to life in a severely stressful environment.</p>
Damaged Wiring<p>Captivity can damage the brain's complex circuitry, including the basal ganglia. This group of neurons communicates with the cerebral cortex along two networks: a direct pathway that enhances movement and behavior, and an indirect pathway that inhibits them.</p><p>The repetitive, <a href="http://dx.doi.org/10.1016/j.bbr.2014.05.057" target="_blank">stereotypic behaviors</a> that many animals adopt in captivity are caused by an imbalance of two neurotransmitters, dopamine and <a href="https://doi.org/10.1016/j.neubiorev.2010.02.004" target="_blank" rel="noopener noreferrer">serotonin</a>. This impairs the indirect pathway's ability to modulate movement, a condition documented in species from chickens, cows, sheep and horses to primates and big cats.</p>
The cerebral cortex, hippocampus and amygdala are physically altered by captivity, along with brain circuitry that involves the basal ganglia. Bob Jacobs, CC BY-ND<p>Evolution has constructed animal brains to be exquisitely responsive to their environment. Those reactions can affect neural function by <a href="https://www.penguinrandomhouse.com/books/311787/behave-by-robert-m-sapolsky/" target="_blank">turning different genes on or off</a>. Living in inappropriate or abusive circumstance alters biochemical processes: It disrupts the synthesis of proteins that build connections between brain cells and the neurotransmitters that facilitate communication among them.</p><p>There is strong evidence that <a href="https://doi.org/10.1523/JNEUROSCI.0577-11.2011" target="_blank">enrichment</a>, social contact and appropriate space in more natural habitats are <a href="https://doi.org/10.1111/j.1748-1090.2003.tb02071.x" target="_blank" rel="noopener noreferrer">necessary</a> for long-lived animals with large brains such as <a href="https://doi.org/10.1371/journal.pone.0152490" target="_blank" rel="noopener noreferrer">elephants</a> and <a href="https://doi.org/10.1080/13880292.2017.1309858" target="_blank" rel="noopener noreferrer">cetaceans</a>. Better conditions <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5543669/" target="_blank" rel="noopener noreferrer">reduce disturbing sterotypical behaviors</a>, improve connections in the brain, and <a href="https://doi.org/10.1038/cdd.2009.193" target="_blank" rel="noopener noreferrer">trigger neurochemical changes</a> that enhance learning and memory.</p>