The efficacy of drugs like Tamiflu - which chemically
interfere with the virus’ ability to reproduce - is
debated. But that doesn’t stop Tamiflu selling out
every time the media calls for a “killer flu season”.SIDE EFFECTS
It’s strange to think that almost every awful
symptom you feel during the flu is the result of
your own body attempting to attack it.
On the other hand, consider what would
happen if your body didn’t react this way. You
wouldn’t get the nagging cough, the aches and
pains, or even the persistent fever. Instead, the
flu virus would continue to replicate and slowly
destroy the lining of the respiratory tract—or
worse, allow bacteria to cause pneumonia and
destroy it irst.
And since you need your respiratory tract to
live, you might not survive to tell the tale. So if
you do end up coming down with the flu and
feel those aches and pains coming on, know
that it’s the only way to get better.
Don’t count your (non-viral) chickens yet,
though. Keep an eye out for a steady recovery
followed by a sudden downturn; that’s a
common sign of pneumonia, which is how
most flu fatalities occur.As for the awful fever and chills, you can
thank those cytokines again. And one speciic
type, interleukin-1, might be the main culprit.
These cytokines are seemingly able to cross
the semipermeable network of capillaries that
connect the brain to the rest of the body (known
as the blood-brain barrier). Inside the brain the
cytokines reach the hypothalamus, your body’s
thermostat, and interfere with its functioning
to crank up the temperature. Once an increased
temperature is induced, the hypothalamus
responds by telling the body to shiver and
restricting blood vessels, as well as creating an
overall feeling of chilliness.
A fever is rare in adults with mere colds, but
almost certain in a person with the flu. This isn’t
true for young children however, especially
infants, in which at least a mild fever frequently
accompanies a cold. Researchers are still pretty
unclear on whether a higher body temperature
itself actually provides any beneit, but it’s at
least a sign that your body is ighting its invaders.
Researchers think this systemic release
of cytokines into the bloodstream directly
influences other flu symptoms, like severe
headache and a lack of appetite, though their
mechanisms aren’t as clear.what’s special about it, and create a unique
molecule on their surface that inds and
destroys similar invaders.
The influenza virus has already started its
own rapid replication by the time this process
gets started, so the adaptive immune system
must generate a lot of T cells to wage a proper
war. This massive production of T cells that
iniltrate your lungs, throat, and nose cause
inflammation, swelling, and pain. In your
lungs, the mucus that accumulates from
the inflammation itself causes you to cough
constantly as your body works to clear airways.
And because your lungs are now damaged
and vulnerable, you have a greater chance of
acquiring pneumonia from an opportunistic
strain of bacteria.
FEEL THE BURN
What about the aches and pains, and especially
the lethargy that sets flu apart from a mere
cold? That’s also your immune system at work.
All those proteins—the cytokines and
chemokines—travel through the bloodstream,
which makes its way to every organ system
in the body. Once they get there, the
inflammatory proteins affect the way many
of those organ systems function, causing
symptoms of the flu.
For example, the aches and pains that
make you feel like you just rain an endurance
run, researchers believe, occur because the
cytokines induce the breakdown of muscle
proteins. Researchers think this breakdown is
likely beneicial, because many of the resulting
amino acids help to create and strengthen
parts of the immune system.
Insight
CYTOKINE STORM
Influenza can be killer (see: 1918), but mostly
its a secondary infection that does the killing.
Sure, the virus can give you pneumonia
directly, but often it just weakens you enough
to allow some other bug to take hold.
But in some cases the mere presence of flu
can cause the immune system to basically
break your blood. It’s called Cytokine Release
Syndrome (CRS), or a cytokine storm.
CRS occurs when white blood cells release
inflammatory cytokines, which in turnactivate more white blood cells. It’s a sort of
chain reaction, which leads to an almost
literal meltdown of the body’s ability to
manage blood oxygen properly.
The result is a cascade of increasingly
severe issues - all caused by the immune
system messing up, rather than the flu - and
it can most definitely be fatal.
Fortunately, CRS is more usually associated
with avian influenza, or bird flu. Even so it’s an
extremely serious condition that, even in a mild
form, can put you in intensive care.28 POPULAR SCIENCE