IT WAS a rare example of a straight-up good news story. 鈥淧olio has been eradicated in the western hemisphere, officials at the Pan American 午夜福利1000集合 Organization declared last week,鈥� we wrote in our 8 October 1994 issue.
Polio is a viral disease that is typically transmitted by the ingestion of faecal matter, often through infected water supplies. If the virus enters the central nervous system, it can cause muscle weakness and paralysis, and sometimes death or long-term disabilities.
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Effective polio vaccines were first developed in the 1950s, but a coordinated global fight to eradicate the disease began in earnest in 1988. The disease was officially eliminated in China, Australia and 34 other western Pacific countries in 2000. Europe was declared polio-free in 2002.
鈥淭he last known polio case in the Americas was a Peruvian boy called Luis Fermin who contracted the virus in August 1991,鈥� we wrote. Models suggested that if the virus were still circulating there, at least one case of polio-induced paralysis would have occurred in the following three years. There had been none.
Other animals can鈥檛 carry polio, so once the world鈥檚 human population is finally purged of it, there will be no reservoir from which the natural virus can emerge to reinfect us. Afghanistan and Pakistan are the last remaining regions with wild polio cases; there are fewer than 100 a year.
Will the scourge of polio now vanish from human memory? Probably not. For a start, there is an attenuated strain present in the popular and effective trivalent oral polio vaccine itself. This strain can persist in the environment and regain the ability to cause polio. Such a strain was probably responsible last month for the first cases of polio recorded in the Philippines since the virus was declared eradicated there in 2000.
We discussed one ingenious solution to this problem in March 2017, when we reported on some nifty gene editing that resulted in a live vaccine with a lower risk of mutating into a virulent form. More worrying, perhaps, is that a team of researchers in 2002 built the polio virus from scratch in the lab, using nothing more than genetic sequence information from public databases and readily available technology. The price of liberty from polio will be eternal vigilance.
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