The polio virus was detected in London sewage for the second time this year, days before ministers withdrew funding for global polio eradication efforts.

Its detection reveals the spending cuts to be “shortsighted and self-defeating”, campaigners said. Polio is an extremely infectious viral disease, which typically affects young children under five. It can cause paralysis by damaging nerves in the spine and base of the brain, and can be life-threatening if it affects muscles used for breathing.

UK health officials take weekly samples of wastewater from sewage plants around England to check for the presence of polio and will typically pick up a handful of cases a year. The latest detection, in a sample collected on 2 March and reported by the Global Polio Eradication Initiative (GPEI) on Friday, is the 10th since 2024.

“The finding, once again, of poliovirus in sewage samples in London indicates there is an ongoing risk that the virus is transmitting in the city. This is a very worrying situation in communities with low vaccination rates, an ongoing danger to health in parts of London, as polio infection can be devastating,” said Prof Sir Andrew Pollard, the director of the Oxford Vaccine Group at the University of Oxford.

Pollard urged parents to check their children were up to date with polio jabs. Mass vaccination programmes have eliminated polio from most parts of the world, but the wild type of the virus is still found in pockets of Afghanistan and Pakistan.

A newer form known as circulating vaccine-derived poliovirus – the kind detected in London – occurs when the weakened vaccine virus used in the oral polio vaccine is excreted in someone’s stool. In communities with low vaccination rates, it can mutate to a form that can cause paralysis. There were 225 cases reported in 2025.

The government announced it was eliminating funding for the GPEI last week, as part of more than £6bn in aid cuts being made to fund an increase in defence spending.

The UK has historically been the GPEI’s second largest government donor after the US. Even before the UK announcement, the initiative said it would have to make significant cuts to surveillance and outbreak response programmes after wider funding cuts meant its 2026 budget was 30% lower than planned.

Adrian Lovett, the UK executive director at One, an anti-poverty campaign group, said: “Covid showed us that viruses do not respect borders. No matter how wealthy a country may be, our defence against public health emergencies depends on our neighbours and we are only ever as strong as our weakest link.

“That is why the UK government’s decision to slash international assistance is so short-sighted and self-defeating. Not only do we have a moral responsibility to the world’s most disadvantaged people, but it also puts the UK public in greater danger.”

Dr Kathleen O’Reilly, an associate professor of epidemiology and population health at the London School of Hygiene and Tropical Medicine, said it was “too soon to tell” whether the detection was likely to indicate a traveller returning from a country where there was polio or where the oral vaccine was in use, or if it indicated early local spread.

It was important to emphasise that a positive sewage sample “doesn’t correspond to a paralytic case”, she said, adding: “UKHSA [UK Health Security Agency] will be working very carefully with hospitals and GP practices to be on extra alert.” However, O’Reilly also said there had been an increase in similar reports from European countries such as Germany.

Polio immunisation coverage has dipped slightly in the UK in recent years, with the percentage of one-year-old children who had received all three recommended doses of the polio vaccine falling from 95% between 2012 and 2015 to 92% in 2022-23.

Dr Vanessa Saliba, a consultant epidemiologist at UKHSA, said: “UKHSA works closely with the MHRA [Medicines and Healthcare products Regulatory Agency] to conduct routine polio environmental surveillance as part of our commitment to global polio eradication. In the UK this year, there have been two unrelated detections of vaccine-derived polio virus type 2 in sewage collected from London Beckton sewage treatment works. One-off detections like this are not unusual. The findings are consistent with importations and there is no evidence of local transmission.

“While the risk to the general public is very low, parents should ensure their children are fully up to date with their polio vaccinations. Check your child’s red book and contact your GP practice to catch up on any missing vaccinations.”

In the US, experts have said they worry that increasing anti-vaccine sentiment will lead to a resurgence of the disease.