Here in the rich countries we hardly even think of polio these days. Back when oldsters like me were young it was still a memory but one kept at bay by Jonas Salk’s polio vaccine. For the generation before it was a horror that swept through the population crippling, paralysing and even killing children. The memory of how awful it was has gone – although we might occasionally think of those like Julian Critchley struck down in old age by post-polio syndrome.
Out there in the wilds things are not so good. As with smallpox there’s been an international campaign to try to rid the world of it entirely. There seems to be no animal reservoir for polio. So, if we wipe it out, just the once, in all humans then it’s gone, entirely and completely. The vaccine is easy enough to administer, this should be possible – as with smallpox.
Our problem is that there are reservoirs of it still. Places where vaccination is not going to plan, like Pakistan:
Extensive environmental surveillance by the Pakistan Polio Eradication Programme has detected poliovirus in the sewage of 10 cities in the last month. According to results shared by the National Emergency Operations Centre, the presence of the poliovirus was confirmed in sewage samples collected from Rawalpindi, Faisalabad, Lahore, Karachi, Sukkur, Killa Abdullah, Quetta, D.I. Khan, Peshawar and South Waziristan in January.
The polio virus does concentrate in excreta. It’s still true that we are warned to be careful changing nappies of those who have just had the vaccine. Sewage works are therefore where to go to survey the population. And it’s there:
A polio case can be reported in any city due to the frequent movement of people from one city to another, but the presence of the virus in sewage water means that a vaccination campaign in the area did not meet its target. The presence of the virus in sewage water also shows that the immunity level of local children has fallen and they are at risk of the disease.
Given the interconnections of the modern world we cannot just hope to wipe polio out locally. Sure, that’s a good start, but we want to make sure that it’s really gone everywhere. Matters aren’t helped by certain clerics in certain places – not Pakistan particularly, I think instead of Afghanistan and parts of Nigeria – claiming that the vaccination is all a plot against religion. But what we’re trying to do is drive that other species, poliovirus itself, extinct. And that really does mean killing it all, everywhere.