[Intro]
As a species, we have an arch nemesis, and we spend a lot of time here on SciShow talking
about it: not mosquitoes, though they definitely do suck, or ticks, or asteroids, or zombie
apocalypses.
I'm talking about viruses.
The US is currently experiencing a textbook case of a virus outbreak.
It's not particularly big or even severe.
Thankfully everyone who has been infected so far has recovered, but it's an object lesson
in what makes viruses such a worthy adversary.
This summer, the US has seen an unusual outbreak of enterovirus, a big, diverse group of viruses
that can cause illnesses ranging from summer colds to polio and hand, foot, and mouth disease.
It also includes D68, a rare, obscure strain that's causing a rash of hospitalizations,
especially among children.
D68 is different from other enteroviruses in that it almost exclusively attacks the
upper respiratory system.
It can cause wheezing, coughing, and flu-like symptoms in young children, but kids with
even mild asthma or other immune disorders may quickly become unable to breathe.
One of the symptoms being reported is that children's lips turn blue, but what's interesting
about this outbreak is how little we know about D68 even though it's not new.
It was first identified in California in 1962, but for the rest of the 20th century, it only
occurred in little pockets, and it was basically written off as a really bad summer cold, but
it's a hearty little sucker.
One trick enteroviruses have that others don't is that they can withstand our stomach acids
and even set up shop in our guts.
Even though the strain we're talking about right now causes respiratory infections, the
"entero" in enterovirus refers to our intestines, but because D68 kept a low profile, it became
so obscure that no one kept any records about how many people were being infected or where.
As a result of this low profile, there's not only no vaccine and no widespread natural
immunity to it, but the organizations that you'd expect to stay on top of this stuff,
like the Centers for Disease Control, turn out to not have any records on the thing,
so when outbreaks of D68 were reported in Japan, the Philippines, and the Netherlands
in 2009, we were caught off guard, and now, it's back in the US, right at the time when
the virus's favorite season, summer, overlaps with the beginning of the school year, providing
lots of nose-picking new hosts.
The CDC doesn't know for sure how many people have been infected, but judging by what hospitals
are reporting in places like Ohio, Illinois, and Missouri, it's probably in the thousands.
The good news is no deaths have been reported in the outbreak, symptoms ease off after a
few days, and officials say the outbreak should die down in late October, when the cold weather
begins: just in time for flu season!
Now, let me take you back to 2012 and one of SciShow's first episodes ever.
It was about overpopulation, and at the time, it was thought that the world's growing population
would level off and stabilize by the year 2050, but according to a new study published
this week in the journal Science, that's probably not the case.
Instead, based on the latest projections from the United Nations, human numbers are expected
to keep growing through 2100.
By then, we're now expected to have anywhere between 9.6 and 12.3 billion people on Earth.
Right now, we've got around 7.2 billion.
So, why has our projected stabilization date extended so far?
Well, the answer lies in the statistic known as total fertility rate.
That's the average number of children a woman has over her lifetime.
The world's total fertility rate has been declining since the mid-1960s due to things
like better access to health care, education for women, and revolutions in contraception,
but in sub-Saharan Africa, the pace of decline has been less than anticipated, and it's declined
less than any other continent.
The average woman there has 4.6 children in her lifetime.
Compare that to the United States, where the average woman has 2.01 children, or Singapore,
where the average woman gives birth to 0.8 children.
That's not even a whole child.
It's eighty percent of a child.
The authors of the new study attribute Africa's higher fertility rate to a couple of factors.
First, for cultural reasons, the notion of the ideal family size tends to be higher in
sub-Saharan Africa than in other regions, but also, limited access to education and
strong economies to work inside of and limited access to contraception leaves few options
for women who don't want to have children, and also, the population is growing because
of lower mortality rates, especially from HIV.
As we talked about a few weeks ago, people are dying less from HIV and living longer,
due in part to better health care, although southernmost Africa still has the world's
highest incidence of the virus, with some countries having more than fifteen percent
of the adult population infected, so more people growing older plus new babies being
born equals a growing population.
Sub-Saharan Africa is now expected to balloon from one billion people now to anywhere between
3.1 and 5.7 billion people by the end of the century.
Thanks for watching SciShow News.
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