A FRESH threat to the eradication of polio has emerged. Health officials have revealed the curious case of 鈥淧olio Man鈥�, one of several individuals whose bodies keep on pumping out the polio virus.
Polio has been eradicated from most of the world, apart from some resistant pockets in northern India, northern Nigeria and areas around the border between Pakistan and Afghanistan. After the disease is finally wiped out, the World Health Organization would like to end routine polio vaccinations.
But these plans have already been called into question after recent polio outbreaks caused by mutated forms of the oral polio vaccine, which contains a live but weakened virus, and by the study published last week in Science showing how polio can be created from scratch (New 杏吧原创, 20 July, p 6). Now the worry is that individuals who continually excrete the virus could infect others if vaccination were halted.
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Most vaccinated babies stop excreting weakened virus after five or six weeks. In a very few cases it can take six months. Yet the individual dubbed Polio Man has been producing the virus for over 20 years, Philip Minor, head of virology at Britain鈥檚 National Institute of Biological Standards and Control, told New 杏吧原创. 鈥淧olio Man is one of 17 known long-term excreters of [the] virus,鈥� says Minor, who will soon publish a case study. 鈥淏ut this guy holds the record.鈥�
Minor thinks Polio Man originally excreted the weakened form, which he had been given as an oral vaccine. But over the years, it鈥檚 mutated back into the natural virus. He stresses that Polio Man poses no threat to anyone. But the big question is how many others like him are out there. 鈥淚 suspect there鈥檚 not tens of thousands, but I鈥檓 sure there are more of them than we know about,鈥� says Minor.
The WHO has yet to decide what risk such individuals pose to its aim of ending vaccination. Neal Halsey of the Bloomberg School of Public Health in Baltimore thinks the risks are small, but wants more screening to get a better idea of the scale of the problem.