Polio in London

28 June 2022

Article: 56/2508

On 22 June 2022, the UK Heath Security Agency (UKHSA), working with the Medicines and Healthcare products Regulatory Agency (MHRA), found poliovirus in sewage samples collected from the London Beckton Sewage Treatment Works. 

As part of routine surveillance, it is normal for one to three vaccine-like polioviruses to be detected each year in UK sewage samples, but these have always been one-off findings that were not detected again. These previous detections occurred when an individual vaccinated overseas with the live oral polio vaccine (OPV) returned or travelled to the UK and briefly shed traces of the vaccine-like poliovirus in their faeces. 

Investigations were launched after several closely related viruses were found in sewage samples taken between February and May. The virus has continued to evolve and is now classified as a vaccine-derived poliovirus type 2 (VDPV2), which on rare occasions can cause serious illness, such as paralysis, in people who are not fully vaccinated. 

The detection of a VDPV2 suggests it is likely there has been some spread between closely linked individuals in north and east London and that they are now shedding the type 2 poliovirus strain in their faeces. The virus has only been detected in sewage samples and no associated cases of paralysis have been reported, though investigations are underway to establish if any community transmission is occurring. Vaccine-derived poliovirus is rare and the risk to the public overall is extremely low. 

The last case of wild polio contracted in the UK was confirmed in 1984. The UK was declared polio-free in 2003, with low-risk for polio transmission due to the high level of vaccine coverage across the population. However, vaccine coverage for childhood vaccines has decreased nationally and especially in parts of London over the past few years, so the UKHSA is urging people to check they are up to date with their vaccines. 

Wastewater surveillance is being expanded to assess the extent of transmission and identify local areas for targeted action. Healthcare professionals have been alerted to these findings so they can promptly investigate and report anyone presenting with symptoms that could be polio, such as paralysis. 

Source: UKHSA, 22 June 2022