TED全球问题:Nina Fedoroff:对抗寨卡病毒和其他由蚊子传播病毒的秘密武器


TED全球问题:Nina Fedoroff: A secret weapon against Zika and other mosquito-borne diseases

Zika fever:our newest dread disease.What is it? Where'd it come from?

What do we do about it?Well for most adults,it's a relatively mild disease —a little fever, a little headache,joint pain, maybe a rash.In fact, most people who get itdon't even know they've had it.But the more we find outabout the Zika virusthe more terrifying it becomes.For example, doctorshave noticed an uptickof something called Guillain-Barrésyndrome in recent outbreaks.In Guillain-Barré, your immune systemattacks your nerve cellsit can partiallyor even totally paralyze you.Fortunately, that's quite rare,and most people recover.But if you're pregnantwhen you're infectedyou're at risk of something terrible.Indeed, a child with a deformed head.

Here's a normal baby.Here's that infantwith what's called microcephaly.a brain in a head that's too small.And there's no known cure.It was actually doctorsin northeastern Brazilwho first noticed, just a year ago,after a Zika outbreak,that there was a peakin the incidence of microcephaly.It took medical doctors another yearto be sure that it was causedby the Zika virus,but they're now sure.And if you're a "bring onthe evidence" type,check out this publication.

So where did it come from,and how did it get here?And it is here.Like many of our viruses,it came out of Africa,specifically the Zika forest in Uganda.Researchers at the nearbyYellow Fever Research Instituteidentified an unknown virusin a monkey in the Zika forestwhich is how it got its name.The first human cases of Zika feversurfaced a few years laterin Uganda-Tanzania.The virus then spread through West Africaand east through equatorial Asia —Pakistan, India, Malaysia, Indonesia.But it was still mostly in monkeysand, of course, mosquitoes.In fact in the 60 years between the timeit was first identified in 1947 and 2007there were only 13 reported casesof human Zika fever.And then something extraordinary happenedon the tiny Micronesian Yap islands.There was an outbreak that affectedfully 75 percent of the population.How did it get there? By air.Today we have two billioncommercial airline passengers.An infected passenger can board a plane,fly halfway around the worldbefore developing symptoms —if they develop symptoms at all.Then when they land, the local mosquitoesbegin to bite them and spread the fever.Zika fever then next surfacedin 2013 in French Polynesia.By December of that year, it was beingtransmitted locally by the mosquitoes.That led to an explosive outbreak in whichalmost 30,000 people were affected.From there it radiated around the Pacific.There were outbreaks in the CookIslands, in New Caledonia,in Vanuatu, in the Solomon Islandsand almost all the way around to the coastof South America and Easter Island.And then, in early 2015,there was an upsurge of casesof a dengue-like syndromein the city of Natalin northeastern Brazil.The virus wasn't dengue, it was Zika,and it spread rapidly —Recife down the coast, a big metropolitancenter, soon became the epicenter.Well people have speculated that it was2014 World Cup soccer fansthat brought the virus into the country.But others have speculated that perhapsit was Pacific Islandersparticipating in championship canoe racesthat were held in Rio that yearthat brought it in.

Well today, this is only a year later.The virus is being locally transmittedby mosquitoesvirtually throughout South America,Central America, Mexicoand the Caribbean IslandsUntil this year, the manythousands of casesthat have been diagnosed in the USwere contracted elsewhere.But as of this summer, it's beingtransmitted locally in Miami.It's here.

So what do we do about it?Well, preventing infectionis either about protecting peopleor about eliminating the mosquitoes.Let's focus on people first.You can get vaccinated.You can not travel to Zika areas.Or you can cover upand apply insect repellent.Getting vaccinated is not an option,because there isn't a vaccine yetand there probably won't befor a couple of years.Staying home isn'ta foolproof protection eitherbecause we now know thatit can be sexually transmitted.Covering up and applyinginsect repellent does work ...

until you forget.

(Laughter)So that leaves the mosquitoes,and here's how we control them now:spraying insecticides.The protective gear is necessarybecause these are toxic chemicalsthat kill people as well as bugs.Although it does take quite a lot moreto kill a person than to kill a bug.These are pictures fromBrazil and Nicaragua.But it looks the same in Miami, Florida.And we of course can sprayinsecticides from planes.Last summer, mosquito control officialsin Dorchester County, South Carolina,authorized spraying of Naled,an insecticide,early one morning,as recommended by the manufacturer.Later that day, a beekeeper told reportersthat her bee yard lookedlike it had been nuked.Oops.Bees are the good guys.The citizens of Florida protested,but spraying continued.Unfortunately, so did the increasein the number of Zika fever cases.That's because insecticidesaren't very effective.

So are there any approaches that areperhaps more effective than sprayingbut with less downsidesthan toxic chemicals?I'm a huge fan of biological controls,and I share that view with Rachel Carson,author of "Silent Spring,"the book that is credited with startingthe environmental movement.In this book she tells the story,as an example,of how a very nasty insectpest of livestockwas eliminated in the last century.No one knows thatextraordinary story today.So Jack Block and I,when we were writing an editorialabout the mosquito problem today,retold that story.And in capsule form, it's that pupae —that's the immature form of the insect —were irradiated until they were sterile,grown to adulthoodand then released from planesall over the Southwest,the Southeast and down into Mexicoand into Central Americaliterally by the hundreds of millionsfrom little airplanes,eventually eliminatingthat terrible insect pestfor most of the Western Hemisphere.Our real purpose in writing this editorialwas to introduce readersto how we can do that today —not with radiationbut with our knowledge of genetics.Let me explain.

This is the bad guy: Aedes aegypti.It's the most common insectvector of diseases,not just Zika but dengue,Chikungunya, West Nile virusand that ancient plague, yellow fever.It's an urban mosquito,and it's the femalethat does the dirty work.She bites to get a blood mealto feed her offspring.Males don't bite; they don't evenhave the mouth parts to bite.A little British company called Oxitecgenetically modified that mosquitoso that when it mates with a wild female,its eggs don't develop to adulthood.Let me show you.This is the normal reproductive cycle.Oxitec designed the mosquito so thatwhen the male mates with the wild femalethe eggs don't develop.Sounds impossible?Well let me show youjust diagrammatically how they do it.Now this represents the nucleusof a mosquito cell,and that tangle in the middlerepresents its genome,the sum total of its genes.Scientists added a single genethat codes for a protein representedby this orange ballthat feeds back on itselfto keep cranking out more of that protein.The extra copies, however,go and gum up the mosquitoes' genes,killing the organism.To keep it alive in the laboratorythey use a compound called tetracycline.Tetracycline shuts off that geneand allows normal development.They added another little wrinkleso that they could study what happens.And that is they added a genethat makes the insect glow under UV lightso that when they released itthey could follow exactly how far it wenthow long it livedand all of the kinds of datafor a good scientific study.Now this is the pupal stage,and at this stagethe females are larger than the males.That allows them to sort theminto the males and the femalesand they allow only the malesto grow to adulthood.And let me remind youthat males don't bite.From there it's pretty simple.They take beakers full of male mosquitoes,load them into milk cartons,and drive around the city,releasing them guided by GPS.Here's the mayor of a cityreleasing the first batchof what they call the "friendly Aedes."Now I wish I could tell youthis is an American city, but it's not.It's Piracicaba, Brazil.The amazing thing is that in just a yearit brought down the casesof dengue by 91 percent.That's better than any insecticidespraying can do.

So why aren't we using this remarkablebiological control in the US?That's because it's a GMO:a genetically modified organism.Notice the subtitle here saysif the FDA would let themthey could do the same thing here,when Zika arrives.And of course it has arrived.So now I have to tell you the short formof the long, torturous storyof GM regulation in the USIn the US, there are three agencies thatregulate genetically modified organisms:the FDA, the Food and Drug Administration,the EPA, the EnvironmentalProtection Agency,and the USDA, US Departmentof Agriculture.Took these folks two yearsto decide that it would be the FDAthat would regulate the geneticallymodified mosquito.And they would do it as a new animal drug,if that makes any sense.Took them another five years going backand forth and back and forthto convince the FDAthat this would not harm people,and it would not harm the environment.They finally gave them, this summer,permission to run a little testin the Florida Keys,where they had been invited years earlierwhen they Keys had an outbreak of dengue.Would that it were that easy.When the local residents heardthat there would be genetically modifiedmosquitoes tested in their communitysome of them began to organize protests.They even organized a petition onthe internet with this cuddly logo,which eventually accumulatedsome 160,000 signaturesAnd they demanded a referendumwhich will be conductedin just a couple of weeksabout whether the trialswould be permitted at all.

Well it's Miami that really needsthese better ways of controlling insects.And there the attitudes are changing.In fact, very recently a bipartisan groupof more than 60 legislatorswrote to HHS Secretary Sylvia Burwellasking that she, at the Federal level,expedite access for Floridato this new technology.

So the bottom line is this:biological control of harmful insectscan be both more effective andvery much more environmentally friendlythan using insecticides,which are toxic chemicals.That was true in Rachel Carson'stime; it's true today.What's different is that we haveenormously more informationabout genetics than we had then,and therefore more abilityto use that informationto affect these biological controls.And I hope that what I've doneis aroused your curiosity enoughto start your own inquiry —not into just GM mosquitoesbut to the other genetically modifiedorganisms that are so controversial today.I think if you do that, and you dig downthrough all of the misinformation,and the marketingon the part of the organic food industryand the Greenpeacesand find the science,the accurate science,you'll be surprised and pleased.

Thank you.


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