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SciShow News explains the science behind the latest efforts to stop the spread of ebola: including airport screenings, treatments for patients, and developments in the search for a vaccine.

Hosted by: Hank Green
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Part 1

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A few weeks ago we gave you a primer on Ebola, the virus responsible for nearly five thousand deaths this year in West Africa. Now with isolated cases popping up in the US and Spain, the question on everybody's mind is, "How do we stop the spread?"

People in the media have been proffering all kinds of sensible- sounding suggestions that turn out to be not so sensible. Like, "Why not screen everybody who's traveling out of the hottest of the Ebola hot-zones?" But also, "What about treating the people who are already infected" and, "Where's the vaccine?"

But the fact is, we're working on all of these things, but, like, science is hard sometimes. In airports around the world, first of all, health officials are screening high-risk passengers traveling from the epicenter of the outbreak, Liberia, Guinea, and Sierra Leone.

They do this using simple infrared thermometers, like the kind in your doctor's office. Fever is one of the earliest symptoms of Ebola infection, so any passenger found to have a temperature higher than 100.4º F is then tested for Ebola virus through a blood test.

But obviously stopping thousands of travelers just to take their temperature leaves loopholes that are big enough to fly jumbo jets through. For one thing, the Ebola virus can incubate in a person's body for up to 21 days. That means a passenger can be infected with Ebola and not show any symptoms for up to three weeks.

And, of course, if someone happens to feel a little bit warm and takes a Tylenol or something, it will reduce the fever, thereby masking the symptom that's being screened for.

So if a fever isn't a reliable indicator of infection, what is? We can always skip to the second step of the screening, a polymerase chain reaction or "PCR" test. It's like, basically, DNA photocopying. PCR works by finding trace amounts of Ebola DNA in a blood sample and replicating it over and over again until there's enough DNA to be detected by a microscope. Because PCR can magnify tiny, trace amounts of Ebola DNA, it's really good at detecting Ebola in patients that aren't showing symptoms yet.

So why not just test everybody's blood who's coming out of West Africa? Because it's extremely impractical. Each test costs around $100 to conduct, each sample of blood needs to be transferred, on ice, to a lab, where lab workers, computers, and other hardware can test it, and even then, it takes several hours to analyze each sample. Also, it isn't perfect. It has a false negative rate of 0.4 percent. That means that out of every one thousand people, four could have Ebola but test negative for it.

The good news, though, is that if a person has Ebola, but they are not showing symptoms, they are not contagious. So even if you're on a flight with somebody who has Ebola, but they don't have the symptoms, they're not going to give it to you. It's not going to keep Ebola out of another country, but it is going to prevent everyone on the plane from getting it.

But we do live in a world where some people are going to get Ebola, so we have to start looking at how we can treat them. Can we help them recover? Again, we have options, and we're using them.

Nina Pham, the Dallas nurse who contracted Ebola, was able to recover, in part, because she was given what's known as a convalescent serum - a serum obtained from someone who had recovered from the same infection. In Pham's case, she was given blood plasma from Dr. Kent Brantly, an American doctor who survived Ebola earlier this year. And Brantly, in turn, survived partly because he received serum from a 14 year old boy he had treated in Liberia. These serums work because a survivor's blood is rich in antibodies that know how to fight the virus. For those individual cases, it was an elegant solution.

But convalescent serums don't always work, and they also run the risk of transmitting other blood-borne diseases, like HIV or hepatitis, to the recipients. Plus there are the enormous challenges of finding a way that's both safe and feasible to bank the blood of people who have survived Ebola. Unsurprisingly, this is much easier to do in America, where we have a complicated medical infrastructure, than it is in, like, West Africa, for example, which is just one of the reasons why Ebola is actually pretty survivable if you have it in America. Unfortunately, the vast majority of people infected with Ebola are not in places with complicated medical infrastructures, so drug companies are developing other therapeutic medicines like the experimental treatment called ZMapp.

ZMapp is made by injecting mice with a protein from the Ebola virus. The mice then produce antibodies to cripple the viral protein, and scientists then genetically modify those antibodies for human use by combining them with fragments of human antibodies. So far this technique has successfully treated primates infected with Ebola, and preliminary results suggest that it's effective in people too.

But still, as promising as all of these treatments sound, we haven't found that silveriest of silver bullets that everybody's looking for, a vaccine. There are actually lots of Ebola vaccines in development right now, but the one that's farthest along is being engineered by a pharmaceutical company, GlaxoSmithKline, with the National Institutes of Health. This vaccine takes a non-lethal virus and splices an Ebola gene into it. When the immune system responds to this non-lethal virus, it develops antibodies that will work against a living Ebola virus. So far this approach has proven successful in protecting primates and other animals. As for people, NIH scientists just began testing it on humans last month and won't have the results until November.

Meanwhile, Canada's public health agency has a similar vaccine that's ready for human testing, but the crazy thing is, their vaccine has been sitting on a shelf for nearly a decade. Scientists tested it successfully on primates in 2005 and published a report about it in the journal Nature. It was all ready for human testing, but there wasn't enough money to fund the trials because Ebola just wasn't that common in 2005. Now that this year's outbreak has killed nearly 5000 people, the World Health Organization has put these vaccines on the fast track. The Canadian government has shipped 800 vials of its vaccine to the WHO in Geneva for testing. And GlaxoSmithKline estimate that it could begin a large-scale human trial involving 12,000 Liberians and 8,000 Sierra Leoneans in January. If the trial is successful, the first vaccine for Ebola could be ready for release by April.

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