Public health authorities in wealthy economies are racing to stop the poliovirus return after it has recently appeared in several countries.

On Friday, New York health officials announced that the poliovirus has been detected in sewage samples, and they were sent to the Centers for Disease Control and Prevention (CDC) to be analyzed amid a doubt that the virus might have been circulated locally. A week before, an unvaccinated adult in Rockland County who suffered from paralysis tested positive for the virus.

Rockland has a surprisingly low immunization rate, and authorities have set up vaccination hubs, distributed leaflets urging people to get jabs, and are considering offering polio booster shots to top up people’s immunity.

While health officials in London too said this week they would offer polio vaccine boosters to hundreds of thousands of children after it was detected in wastewater, a cluster was detected in Ukraine as well. concerns have been raised that global conflicts and vaccine hesitancy could lead the disease that was almost globally eradicated to return.

Polio was one of the most feared childhood diseases, not only because it can be fatal, but also because it disabled tens of thousands of people every year for much of the 20th century. It was only due to a global campaign against the disease and the development of a vaccine in the early 1950s that the number of infections dropped.

However, health officials raised the alarm because of its reemergence in Europe and the US and because inoculation programs have been disrupted by the Covid-19 pandemic and by war in countries like Ukraine and Afghanistan.

“There has been a huge dip globally in the routine immunisation coverage, as countries were engaged in the Covid-19 pandemic response. If you scratch the surface, this shows the vulnerability of countries’ immunisation systems,” said Siddhartha Datta, the World Health Organization’s regional advisor for vaccine-preventable diseases in the European region.

Dr. Mary Leahy, chief executive of Bon Secours Charity Health System, said the virus had probably infected a significant number of people without them knowing since three-quarters of those with infections are asymptomatic.

“They have polio, but they’re walking around and do not know that they have it. Only about 25 per cent develop flu-like symptoms... less than 1 per cent go on to develop paralysis.”