The United Kingdom’s health authorities have stated that they are examining a rare polio virus detection in sewage samples in London, which might jeopardise the country’s polio-free status for the first time in nearly two decades.

Between February and May, a number of waste samples from the Beckton sewage treatment plant in Newham, east London, tested positive for vaccine-derived polio virus, according to the United Kingdom Health Security Agency.

The virus has since evolved and is now categorised as a “vaccine-derived” polio virus type 2, according to the UKHSA, who is also investigating whether community transmission is taking place.

The agency has declared a national incident and notified the World Health Organization.

“We are urgently investigating to better understand the extent of this transmission and the NHS has been asked to swiftly report any suspected cases to the UKHSA, though no cases have been reported or confirmed so far,” Dr. Vanessa Saliba, consultant epidemiologist at UKHSA, said Wednesday.

Polio is a rare virus that can cause significant sickness, such as paralysis, in persons who have not been fully immunised. Polio was once endemic in the United Kingdom in the 1950s, but the country was proclaimed polio-free in 2003.

The UKHSA stated that the danger to the general public is extremely low, but parents should ensure that their children are adequately inoculated against the disease. In the United Kingdom, it is normal practise for children to receive an inactivated polio vaccine as part of their routine vaccination schedule, with three injections given before the age of one and additional shot given between the ages of three and fourteen.

“Most of the U.K. population will be protected from vaccination in childhood, but in some communities with low vaccine coverage, individuals may remain at risk,” Saliba said.

Every year, one to three “vaccine-like” polio viruses are found in Britain’s sewage system.

Such detections have always been one-time events, occurring when a person immunised overseas with the live oral polio vaccine returned or flew to the United Kingdom and briefly “shed” traces of the vaccine-like polio virus in their faeces.

This is the first time, however, that a cluster of genetically connected samples has been detected consistently over several months.

Scientists believe this indicates a community spread among closely related individuals in north and east London. According to the UKHSA, the virus has only been found in sewage samples so far, and no cases of paralysis have been reported.

While polio vaccine is prevalent in the United Kingdom, immunisation rates vary across the country, with groups with lower uptake at greater risk.

Vaccine coverage, particularly for childhood vaccines, has declined nationally and particularly in sections of London in recent years.

The National Health Service of the United Kingdom recommends that parents contact their doctor’s clinic to ensure that their child’s immunizations are up to date.

“The majority of Londoners are fully protected against Polio and won’t need to take any further action, but the NHS will begin reaching out to parents of children aged under 5 in London who are not up to date with their Polio vaccinations to invite them to get protected,” Jane Clegg, chief nurse for the NHS in London, said.

“Meanwhile, parents can also check their child’s vaccination status in their Red Book and people should contact their GP surgery to book a vaccination, should they or their child not be fully up to date,” she added.

Britain moved from an oral polio vaccine to an inactivated polio vaccine, which is administered via injection and prevents infection, in 2004.

In most cases, persons who have polio show no symptoms, however some may develop a flu-like disease up to three weeks later. In rare circumstances, the virus can cause paralysis by attacking nerves in the spine and base of the brain. It can occasionally affect breathing muscles, which can be fatal.

Early diagnosis of the virus, according to medical authorities, is critical for tracking its progress and averting more serious instances.

“In populations with low vaccine uptake it is possible that the live polio vaccine can spread from one person to another. If this is sustained, over time (one or two years) this vaccine derived virus can mutate to become fully virulent again and can start to cause paralysis in people who have not been vaccinated,” said Paul Hunter, professor of medicine at the University of East Anglia.

(Adapted from TheGuardian.com)

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