Death knells are beginning to ring for poliovirus. The CDC reports that, in 2014, there were 359 new cases of wild poliovirus in nine countries. Just one year later, the number of new cases dropped to 74, a nearly 80% reduction. Furthermore, the cases were limited to just two countries, Afghanistan and Pakistan. (See figure.)
Wild poliovirus comes in three types: WPV1, WPV2, and WPV3. The latter two have been eradicated (though WPV3 hasn’t yet been officially declared so). The only wild poliovirus left in the world is WPV1.
(Note: Scientists distinguish between “wild” poliovirus and “vaccine-derived” poliovirus. In rare cases, the weakened virus used to vaccinate against polio mutates and causes full-blown polio. However, as the World Health Organization notes, vaccinations have prevented 13 million cases of polio but caused only 760 cases.)
From January 1 to May 4 of this year, merely 15 new cases of polio have been reported; 12 of them were from WPV1, and the other three were from the vaccine-derived variety (which occurred in Laos). Though polio transmission tends to worsen later in the summer and autumn, these numbers are highly encouraging. During the same period in 2015, there were 24 new cases of polio, meaning that public health officials have seen yet another 38% reduction in the number of new cases.
Given current trends, it is entirely plausible that 2017 will be the first year in which no new cases of either wild or vaccine-derived poliovirus occur. If that happens, following the requisite three-year waiting period, polio may be declared eradicated by 2020.
At least two things could prevent this.
First, the hardest part of any eradication effort is quenching the last few remaining cases. All it takes is for one child to get sick, and if others in his community are not properly vaccinated, an outbreak can occur.
Second, religious fanatics, such as Islamist militants in Pakistan, are so opposed to polio vaccines that they have killed public health officials who try to administer them. In their twisted worldview, polio vaccines are a “conspiracy of Jews and Christians to make Muslims impotent and stunt the growth of Muslims.” (Does such conspiracy theorizing sound familiar?)
On the bright side, the Islamic State (ISIS) appears to take polio seriously. ISIS allowed public health officials to perform a mass vaccination campaign in Syria. According to Vox, this was borne out of the belief that “polio is bad and vaccines are good.”
It's rather pathetic that, on the topic of vaccination, some of us in the West could actually learn something useful from ISIS.
Source: Centers for Disease Control and Prevention. "Progress Toward Polio Eradication — Worldwide, 2015–2016." MMWR 65 (18): 470-473. May 13, 2016.