And the video went viral.

The world has never seen this virus before this B cell, it'll bump into this virus and this virus won't attach.

I bet you got a touch of that virus been going around.

The first problem we ran into was that, in these last four countries, the strongholds of this virus, we just couldn't seem to get the virus rooted out.

This virus can only survive in people.

Thus, its genome is far less densely packed than any other known virus.

Maybe it's this one.

So we are trying to wipe out this virus completely.

So things were looking very exciting, and then about five years ago, this virus, this ancient virus, started to fight back.

He's going to say, look, I'm the guy that can match this virus here and so he's going to start cloning himself.

To begin with, I came to work with this virus that causes that ugly tumor in the chicken.

This is one of the very few viruses in the world where there are big enough cracks in its armor that we can try to do something truly extraordinary.

And as long as any child anywhere is paralyzed by this virus, it's a stark reminder that we are failing, as a society, to reach children with the most basic of services.

If this virus was in thousands of individuals at this point, why was it the case that it took us until 1984 to be able to discover this virus?

And then to make the matters even worse, the virus started to spread out of these four places, especially northern India and northern Nigeria, into much of Africa, Asia, and even into Europe, causing horrific outbreaks in places that had not seen this disease for decades.

In Umar's home country of Nigeria, a 95 percent reduction in the number of children paralyzed by polio last year.

When we started, over 20 years ago, 1,000 children were being paralyzed every single day by this virus.

If this virus was in thousands of individuals at this point, why was it the case that it took us until 1984 to be able to discover this virus?

And not only that, but when they came into these countries, then they got on commercial jetliners probably and they traveled even farther to other places like Russia, where, for the first time in over a decade last year, children were crippled and paralyzed by a disease that they had not seen for years.

And as long as any child anywhere is paralyzed by this virus, it's a stark reminder that we are failing, as a society, to reach children with the most basic of services.

And maybe several thousands of B cells will bump into this virus and it won't attach, but since I have so many B cells having so many different combinations of these variable portions on these receptors, eventually one of these B cells is going to bond.

And then to make the matters even worse, the virus started to spread out of these four places, especially northern India and northern Nigeria, into much of Africa, Asia, and even into Europe, causing horrific outbreaks in places that had not seen this disease for decades.

And not only that, but when they came into these countries, then they got on commercial jetliners probably and they traveled even farther to other places like Russia, where, for the first time in over a decade last year, children were crippled and paralyzed by a disease that they had not seen for years.