AS POLIO re-enters the Indonesian capital Jakarta, and the World Health Organization admits it will not eradicate the disease this year, a more subtle problem has cropped up in Slovakia.
The location seems unlikely. Slovakia鈥檚 last polio case was in 1960, and 97 per cent of Slovaks are vaccinated against the disease. But therein lies the problem. The normal vaccine contains live, weakened polio virus, which vaccinated people excrete in their faeces. It can theoretically persist in sewers, where it may revert to the pathogenic form.
This only happens rarely. But this week in the European disease bulletin Eurosurveillance, Eva M谩derov谩 and colleagues at the Slovak Public Health Authority report that 72 different strains of mutated vaccine virus have now been found in sewage systems, some almost identical to wild polio virus.
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While there have been no known cases of people being infected, the source of the virus remains unknown. No people with weakened immunity, thought to be potential sources for such mutant vaccine viruses, have been found to be excreting polio.
鈥淰accinated people excrete live polio virus in their faeces, and it can persist in sewers鈥�
Slovakia has quickly switched to a killed polio vaccine, which it hopes will end the problem.
