There’s really no good way to say this, so I’m just gonna go for it: an unexpected
consequence of spaceflight is herpes.
A research team has unveiled interesting results about the presence of herpes in astronauts
that not only shed light on human health in space, but also tell us some important things
about the virus here on Earth, too.
Herpes may be infamous for being a sexually transmitted disease that you can never get
rid of, but it’s actually a lot more complicated than that.
There are over 100 different kinds of herpesvirus that all behave in really different ways,
and 8 of them regularly infect humans.
So when we say that astronauts are getting herpes in space, that doesn’t really mean
what may immediately jump to mind.
Plus, that statement is also technically incorrect—astronauts aren’t getting herpes in space, they already
had it.
It’s just that space is making the virus behave weirdly in our bodies because herpes
is a really interesting virus.
Over 90% of us have herpes, you guys, we just don’t know it because for the most part,
the virus hangs out in a dormant state in your body—that’s what we call a latent
virus, hiding out somewhere just waiting to be woken up again.
Take chicken pox, for example, or VZV.
After you’re initially infected, that virus lives and replicates in the tissues and membranes
in your nose and mouth.
The active virus causes that characteristic itchy polka dot rash, and during this phase,
you are actively shedding viruses.
If someone else comes into contact with your mucus or the fluid leaking from your chickenpox
blisters, they’re coming into contact with active virus and are likely to get sick themselves.
About a week later, in most cases, your symptoms have improved and you’re all better!
But...the virus is still there.
See, herpesviruses inject their own DNA into your cellular machinery to travel from the
tips of nerves, to the nuclei, of say, your cranial nerves in the case of VZV.And the
virus stays there for the rest of your life.
When your body is stressed, your immune function declines.
And when your immune system lets its guard down, anything that was previously just chillin’
in your body may start to cause some problems.
So, if we stick with our chickenpox example, immunocompromised populations like the elderly
are at high risk of developing shingles, another form of expression for ZVZ, because their
immune systems are more fragile and the virus gets the chance to rear its ugly head again.
And what could be more stressful to your body than space?
This new study found that during space flights as short as ten days and as long as several
months, astronauts were shedding four of the main eight herpes viruses found in humans,
and shed them in way larger quantities than they did before or after their missions.
Shedding levels were high enough to mean that in over half of the tested astronauts, herpesviruses
were reactivated and this was sometimes even accompanied by physical expression of the
virus, resulting in cases of shingles for several crew members.
This work builds on our increasing base of knowledge telling us that spaceflight is extremely
stressful to the human body—from increased radiation exposure to the physiology-altering
effects of microgravity to the social isolation—and therefore spaceflight alters immune function
in important ways.
Viral reactivation in these astronauts was accompanied by higher levels of stress hormones,
like cortisol and epinephrine, and the longer the mission, the higher the stress hormones
and the more virus the astronauts shed.
This is something that will be a huge consideration as we figure out how to keep humans healthy
for longer space missions.
And herpesvirus reactivation in particular makes astronauts less resilient to any other
physical challenges they may face in space .
Since we know herpesviruses like ZVZ can live in our cranial nerves—you know, the ones
connected directly to our brains that we use to move our bodies and sense the world around
us—this viral reactivation problem in astronauts could even present some risk of permanent
vision and hearing loss during long-term spaceflight.
All this research is doubly important because it gives us key insight into how viruses behave
in immunocompromised patients.
So, this stuff isn’t just relevant for astronauts—it also lets us better treat and care for vulnerable
populations who may be suffering from viral reactivation here on Earth.
If you want more first-of-its-kind info on how spaceflight affects the human body, check
out my video here on the results of NASA’s first ever space twin study, and make sure
you subscribe for all your viral science news.
And while you’re at it, you can check out our new show Sick for more on viruses.
As always, thanks for watching.