[pbs digital studios intro] this episode is sponsored by audible [iotbs intro] [epic music] the roman empire… at its height, home toone in five people on earth. but add in a few hundred years of corrupt decadence andbarbarian 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 airâ€. wrong reason, right words. dna pulled from5th century graves near rome matched the parasite that causes malaria, and once scholars startedlooking, they realized the spread of malaria was a big reason the empire went to ruin. after they connected the world, romans broughthome more than they bargained for: a disease that targets children and the poor, and theinsects that help it spread. and that’s what brings us to zika [news reports]
when the zika virus was declared a globalpublic health emergency in february 2016, this was all that scientists had ever writtenabout 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 flavivirusrelatives, it looks like an awesome soccer ball, but is considerably less fun to playwith. over the next 60 years, zika popped up in the odd monkey or mosquito, but priorto 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, whenbrazil noticed thousands of babies born with
abnormally small heads and brains. there’snow little doubt that zika is directly to blame.unlike most viruses, not only can zika cross the placenta from mother to child, but wenow know it specifically targets developing brain cells. worse, zika also kills radialglial 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 knowthey have it. the world health organization has resorted to telling women in zika-affectedareas “don’t get pregnantâ€, which is a pretty good sign we don’t have any goodoptions. of course the virus can’t do all this onits own. a few cases of sexual transmission
aside, almost everyone who’s caught zikagot it from one of these. only a tiny fraction of the more than 3,000known mosquito species bite humans, but aedes aegypti is one of the worst. it feeds duringthe day, it likes being indoors, it even sneaks up on people from behind. every mosquito breedsin standing water, but even a discarded candy wrapper can hold enough for aedes to lay itseggs. of course that doesn’t even matter, because aedes eggs can be dried out for monthsand still hatch. zika has continued to march north, and theu.s has seen a few hundred cases in travelers returning from zika areas, including nearly200 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’sa 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 thevirus, there isn’t much of north america or europe that is out of reach. to keep the virus from gain a foothold, thesecret is to keep from getting bit. mosquitoes can’t pass it to each other, they need usin between. there’s still a lot of unanswered questionsabout zika, but the biggest is why now? well, the world’s a very different placethan it was 50 years ago. there’s more people, and they live closer.together than ever before.
we migrate on massive scales, whether it’sthe olympics or refugees fleeing war. perfect ingredients for an outbreak. it’s likelyzika always had the potential to be dangerous, it just never got the chance. and it’s not just zika. we’re seeing moreweird 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 yearanother tropical disease pops up out of seemingly nowhere and we’re caught off guard.. the biggest risk factor for these diseasesisn’t geography or genetics, it’s poverty.
zika thrives when there’s lots of peoplearound to bite, but it helps if they don’t have windows on their houses, or their neighborhoodis 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, strikepoor people in the 20 richest nations on earth. in houston’s 5th ward, doctors are alreadyfinding diseases like dengue, leishmaniasis… and the ingredients are perfect for zika tocheck in. we should develop vaccines and drugs to fightzika, 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 theromans have taught us anything, it’s that
everyone is vulnerable, no matter how highon the hill you build your house. stay curious
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