Of course, polio exists in other parts of the world. A global campaign to eradicate it has been working on this grueling task since 1988. Last year, the polio virus caused paralysis—which cannot be treated or cured—in two countries where it was never fought and in 21 others where it recovered. Disease experts, however, were not surprised to see its re-emergence in Western nations. For years they have watched protection against the disease undermined by funding cuts, vaccine reluctance, forgetfulness — and the insidious nature of the virus. “This should be a wake-up call for people,” says Heidi Larson, professor and founder of the Vaccine Confidence Project at the London School of Hygiene and Tropical Medicine. “We’ve said that until we can completely eradicate it, we’re all at risk.” Public health experts see this as an urgent need because cases of polio paralysis represent the tip of an immune iceberg: For every paralyzed person, at least several hundred are likely to have asymptomatic infections, providing a haven for the virus to replicate and spread. This takes time. The sewage findings indicate that polio has probably been circulating since February in London and for at least several months in New York. That sense of urgency is why London’s health authorities have offered booster shots to children aged 9 and younger, and why their counterparts in New York – where 40 per cent of children in some zip codes are unvaccinated – urged parents to bring children for shots. “The number one way to prevent paralytic polio is to get vaccinated against the polio virus, and the vaccine is more than 99 percent effective at preventing paralysis,” says Daniel Pastula, MD and associate professor at University of Colorado Anschutz Medical Campus studying neuropathy. – invasive diseases. “If you are not vaccinated or your children are not vaccinated against polio and the polio virus is circulating in your community, you are at risk of developing paralytic polio.” To understand how polio ended up in these cities, it helps to review a little history. Two stories, actually: one about the polio vaccine and one about how it was used to eradicate the disease from the world. Start with the vaccine formula — or formulas, actually, because there are two. They were born out of a fierce rivalry in the mid-20th century between scientists Jonas Salk and Albert Sabin. Salk’s formula, the first to be approved, is given by injection. it uses an inactivated version of the virus and protects against the development of disease, but does not stop the transmission of the virus. Sabin’s formula, which came a few years later, used an artificially weakened live virus. It blocks transmission and—because it’s a liquid that’s put into a child’s mouth—it’s cheaper to make and easier to distribute, since it doesn’t require trained doctors or careful needle disposal. These properties made Sabin’s oral version, known as OPV, the mainstay of polio control and ultimately the main weapon in the global eradication campaign.
