The last wild-type polio infection in Nigeria occurred on July 24, 2014. The last one in Somalia occurred August 11, 2014. No other country in Africa has seen a polio case, so that means the entire continent has been polio-free for one year. If it can make it another two, the authorities will declare the continent polio-free.
This is exciting, because it means we are a step closer to eradicating the disease, and the day when vaccination against it will no longer be necessary. Only two countries in the world still have endemic polio: Afghanistan and Pakistan. With luck and hard work, the virus can be eliminated there as well and we will have managed the third extermination of a virus by vaccination. The others are smallpox and rinderpest, a bovine infection similar to measles that was eliminated by livestock vaccination.
There are other diseases we could wipe out. Dracunculiasis is nearly eradicated, and will probably be wiped out before polio — however, it is not viral (it’s a huge parasitic worm, the guinea worm — stuff of nightmares, really) and there is no vaccine. There have been just a handful of cases this year, so we’ve got this one seriously up against the ropes. Like a virus, the goal in an eradication campaign is to interrupt transmission; it cannot live without a host. Unlike a virus, its much simpler to keep it out — all you need is clean drinking water, or even a fairly coarse filter so you don’t accidentally drink infected water fleas (which are an intermediate host of the organism).
Once we wipe out the guinea worm and polio, our next target is probably measles. Like polio and rinderpest, it can only infect humans, and this gives us the chance to vaccinate enough of the potential hosts that we can interrupt transmission. But we are much further away from wiping out measles. It is no longer endemic in the US, Mexico, Canada, or many other nations, but it’s incredibly infectious, so it only takes one infected person entering the country to spark off a brief outbreak. But we wiped out its close cousin, rinderpest. We can wipe out measles too, and then nobody will ever need a vaccine against it again.