[PBS Digital Studios Intro]
This episode is sponsored by Audible
[IOTBS Intro]
[EPIC MUSIC]
The Roman Empire… at its height, home to one in five people on Earth. But add in a
few hundred years of corrupt decadence and barbarian invasions, and oh how the mighty
do fall. Attila the Hun was bad enough, but Rome had
another enemy on the inside.
The city of ancient Rome was a lot like Hollywood: Rich people partied in the hills, poor people
lived down below… until they died young. Most likely cause of death? Fevers caused
by “bad air”.
Wrong reason, right words. DNA pulled from 5th century graves near Rome matched the parasite
that causes malaria, and once scholars started looking, they realized the spread of malaria
was a big reason the empire went to ruin.
After they connected the world, Romans brought home more than they bargained for: a disease
that targets children and the poor, and the insects that help it spread.
And that’s what brings us to Zika
[NEWS REPORTS]
When the Zika virus was declared a global public health emergency in February 2016,
this was all that scientists had ever written about it, but we’ve learned a LOT more in
the months since.
Here’s the facts: Zika gets its name from the forest in Uganda
where it was first isolated. Like its Flavivirus relatives, it looks like an awesome soccer
ball, but is considerably less fun to play with. Over the next 60 years, Zika popped
up in the odd monkey or mosquito, but prior to a 2007 outbreak on the Pacific island of
Yap, only 14 human cases had ever been reported.
Of course that all changed in late 2015, when Brazil noticed thousands of babies born with
abnormally small heads and brains. There’s now little doubt that Zika is directly to
blame. Unlike most viruses, not only can Zika cross
the placenta from mother to child, but we now know it specifically targets developing
brain cells. Worse, Zika also kills radial glial cells, which normally act as a scaffold
to shape the developing brain. There’s no treatment or vaccine, and symptoms
are usually so mild most people don’t know they have it. The World Health Organization
has resorted to telling women in Zika-affected areas “Don’t get pregnant”, which is
a pretty good sign we don’t have any good options.
Of course the virus can’t do all this on its own. A few cases of sexual transmission
aside, almost everyone who’s caught Zika got it from one of these.
Only a tiny fraction of the more than 3,000 known mosquito species bite humans, but Aedes
aegypti is one of the worst. It feeds during the day, it likes being indoors, it even sneaks
up on people from behind. Every mosquito breeds in standing water, but even a discarded candy
wrapper can hold enough for Aedes to lay its eggs. Of course that doesn’t even matter,
because Aedes eggs can be dried out for months and still hatch.
Zika has continued to march north, and the U.S has seen a few hundred cases in travelers
returning from Zika areas, including nearly 200 pregnant women. So will Zika start spreading
locally? That depends. We have the mosquitoes: Aedes aegypti was accidentally imported decades
ago and is present across the South, and there’s a good chance it’s more widespread relative
Aedes albopictus could also carry the disease, just not quite as well. If colder-climate
species like Culex are able to pick up the virus, there isn’t much of North America
or Europe that is out of reach.
To keep the virus from gain a foothold, the secret is to keep from getting bit. Mosquitoes
can’t pass it to each other, they need us in between.
There’s still a lot of unanswered questions about Zika, but the biggest is why now?
Well, the world’s a very different place than it was 50 years ago.
There’s more people, and they live closer. together than ever before.
We migrate on massive scales, whether it’s the Olympics or refugees fleeing war. Perfect
ingredients for an outbreak. It’s likely Zika always had the potential to be dangerous,
it just never got the chance.
And it’s not just Zika. We’re seeing more weird outbreaks in general: Dengue, chikungunya.
Schistosomiasis, a parasite carried by snails, is now second honly to malaria. Yeah, bet
you never thought you had to worry about snails… And have we forgotten about Ebola?
It’s a scary new pattern: every year another tropical disease pops up out of seemingly
nowhere and we’re caught off guard..
The biggest risk factor for these diseases isn’t geography or genetics, it’s poverty.
Zika thrives when there’s lots of people around to bite, but it helps if they don’t
have windows on their houses, or their neighborhood is full of trash.
You might think these problems are far away, but most of the world’s neglected diseases,
from Zika to that one with the snails, strike poor people in the 20 richest nations on Earth.
In Houston’s 5th Ward, doctors are already finding diseases like dengue, leishmaniasis…
and the ingredients are perfect for Zika to check in.
We should develop vaccines and drugs to fight Zika, but there will be another Zika, or Ebola,
or weird snail parasite to take its place. Maybe the best way to keep people healthy
is to help them live better, because if the Romans have taught us anything, it’s that
everyone is vulnerable, no matter how high on the hill you build your house.
Stay curious