Why Polio, Once Nearly Eradicated, Is Rebounding

Polio has been a cause of life-threatening paralysis for thousands of years. At the height of the biggest-ever outbreak, in 1952, almost 60,000 cases with more than 3,000 deaths were reported in the US alone. A decades-long push to increase immunizations and access to clean water has meant that mass outbreaks, with hospital wards filled with children kept alive in iron lungs, are a distant memory. But while polio was brought to the brink of global eradication, it’s been bouncing back, radiating out from reservoirs in Pakistan and Afghanistan, where conflict and resistance to vaccination have kept the virus circulating. The disruptions of the Covid-19 pandemic and one vaccine’s weaknesses have played a role. Outbreaks in 2022 in the US, the UK and Israel, which had all eliminated polio decades earlier, showed that nowhere was safe and added urgency to the effort to round up funds for a renewed push.

Poliomyelitis is a highly infectious disease caused by one of three poliovirus types. Once inside the body, the virus can invade the nervous system and cause paralysis in a matter of hours. In other cases, symptoms can take as many as 30 days to appear. Initial signs include fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs. Most infections, though, are asymptomatic, a fact that makes it more difficult to prevent transmission, which usually takes place via fecal matter. About one case in 200 leads to irreversible paralysis, usually in the legs. Among those paralyzed, 5% to 10% die when their breathing muscles become immobilized. There is no cure for paralytic polio and no specific treatment. Polio mainly affects children younger than 5, though anyone who is unvaccinated can contract it. In the long term, 25% to 40% of children who recover from paralytic polio get post-polio syndrome, a group of potentially disabling symptoms including weakness and fatigue that appear as long as 15 to 40 years after a patient’s recovery.