Virus wiped out 40 years 'resurrects' in UK

Health officials have warned of a resurgence of polio after traces of the virus were found in London sewage samples.

Although no official cases have been detected, officials have called it a "national incident" and urged people to get vaccinated to prevent the virus from spreading.

Scientists discovered a strain of polio virus in sewage in North and East London in February, a source of wastewater for 4 million people.

Initially, they were not too concerned. However, in April and May, experts noted mutant versions of the virus within the same strain, suggesting that there had been continuous transmission between many individuals over several months. This allowed the virus to evolve. Officials conducted localized testing in six areas of the capital to identify the outbreak.

In the UK, people are vaccinated with an inactivated vaccine that cannot be excreted in their stools or urine. However, some countries around the world use an oral polio vaccine that contains three strains of live, weakened virus. They can shed the virus in their stools for a short time.

Scientists speculate that a traveller or immigrant from abroad had received polio vaccine before arriving in the UK, and that the virus was found in the sewage system. The person may have lived in Nigeria, Pakistan or Afghanistan, where the disease is still endemic.

According to Vanessa Saliba, consultant epidemiologist at the UK Health Security Agency (UKHSA), vaccine-derived polio virus has the potential to spread, especially in communities where vaccination rates are low.

"In rare cases it can cause disease in unvaccinated people. So if your child has not had the polio vaccine, contact your GP immediately to do this," she said.

Paralyzed patients are fitted with chest ventilators to help them breathe normally. Photo:Hulton Archive

Health experts are also concerned that doctors may no longer recognise the symptoms of polio, as it has not been endemic for decades, meaning cases could be misdiagnosed. Officials are urging GPs to be alert to unusual symptoms and report suspected cases promptly.

Polio is spread mainly by an infected person not washing their hands properly and then touching someone else's food or drink. The virus thrives in the intestines and is found in feces. In about 1% of patients, the virus can infect the spine and cause paralysis.

Most patients have no symptoms, said Dr David Heymann, an infectious disease expert at the London School of Hygiene and Tropical Medicine.

UKHSA said that if a specific outbreak is detected, authorities will organise a mass vaccination campaign to protect the community.

Jane Clegg, chief nurse at the National Health Service (NHS), said: "The majority of Londoners are safe from polio and do not need to take any further action. However, the NHS will start contacting parents of children under five in London to update them on the vaccination programme."

Polio has been eliminated from every country in the world except Afghanistan and Pakistan. However, vaccine-derived polio continues to cause small outbreaks, especially in communities or populations with low vaccination rates, such as children.

According to British experts, the community transmission is most likely to have occurred in young children. Less likely is that it occurred from an immunocompromised person who had the virus for many months.