Polio has been largely eradicated around the world, thanks to vaccines developed in the 1950s, first by Jonas Salk and later by Albert Sabin. But in 2010, 445 people of Pointe-Noire, Republic of the Congo were infected by a polio outbreak. Almost half of the infected died.
Now, researchers at France's Institut de Recherche pour le Développement have identified the offending strain of polio. In a paper published this week in the journal PNAS, IRD researchers say the high mortality rate of the Congolese outbreak was in part due to a new strain of polio resistant to current vaccines.
Health officials initially blamed the especially deadly outbreak on poor vaccination coverage, but new DNA analysis of the offending polio strain suggest the virus has genetically evolved to better disguise itself and evade the antibodies produced by a vaccinated immune system.
Researchers tested the new strain on blood samples from vaccinated study participants in both Gabon, Congo's African neighbor, and Germany. The blood samples were less effective at warding off this particular strain of polio than they were at battling others.
Researchers worry other vaccine-resistant strains of polio are lurking out there in nature, and could strike again. They warn that poorly vaccinated communities are especially vulnerable and that doctors and health officials should remain vigilant.
Though the occasional polio outbreak still surfaces, the disease is rarer and rarer. According to the World Health Organization, in 1988 there were a reported 350,000 cases of polio. In 2013, there were just 416.
But researchers responsible for this newest polio study suggest those positive trends could be undermined by vaccine-resistant strains, should health officials lose focus of a disease now largely absent from the public consciousness.