Research and analysis

HPR volume 18 issue 11: news (10 December)

Updated 10 December 2024

Poliovirus detected in routine sewage surveillance from Leeds, London and West Sussex in November

Routine environmental surveillance for poliovirus (PV) is undertaken by the UK Health Security Agency (UKHSA), working with the World Health Organization (WHO) Polio Global Specialised Laboratory at the Medical and Healthcare products Regulatory Agency (MHRA). The surveillance is undertaken at 26 sites, with monthly sampling, across England. It is part of the UK’s commitment to the Global Polio Eradication Initiative and provides an early warning system of PV importations which may then lead to community transmission.

Testing of the samples by the MHRA during November 2024 has identified a Vaccine Derived Poliovirus Type 2 (VDPV2) in 1 sample from East Worthing Sewage Treatment Works (which covers some of West Sussex local authority and adjacent areas), in 2 samples from Leeds Knostrop Sewage Treatment Works and 1 sample from the London Beckton Sewage Treatment Works.

The PV isolates found are genetically linked to a VDPV2 that has been widely circulating in several African countries in recent months, unrelated to any previous PV found in the UK. The same circulating VDPV2 strain has also been recently found in sewage samples from sites from three other European countries, as reported by WHO (1).

To date there is no evidence of community transmission and the risk to the public is low.

As part of routine surveillance, PVs are detected from time to time; these are normally one-off findings due to:

i) individuals being vaccinated overseas with the live attenuated oral polio vaccine (OPV), entering the UK and briefly ‘shedding’ traces of the ‘vaccine-like’ poliovirus in their faeces. Several countries offer OPV on exit as part of their response to polio outbreaks. Individuals who are immunosuppressed may shed virus for a long period of time.

ii) visitors entering the UK from a country where vaccine derived polio viruses have been circulating.

When there is community transmission the PV would be detected over a period of weeks and months. One-off or brief detections do not require any public health action.

Sampling at the sites where the VDPV2 has been detected has increased to fortnightly to inform a timely investigation and any necessary response.

Whilst there is currently no evidence of community transmission, vaccine-derived poliovirus, like the ones detected, have the potential to spread, particularly in communities where vaccine uptake is lower. On rare occasions it can cause paralysis in people who are not fully vaccinated. These latest findings are a timely reminder of the importance of local areas ensuring any children not fully up to date with their polio vaccinations are caught up.

The UK switched from using OPV to Inactivated Polio Vaccine (IPV) in 2004, the year after poliovirus was declared eradicated in the WHO European region. The primary course of polio containing vaccines is offered routinely to all babies at 8, 12 and 16 weeks of age (DTaP/IPV/Hib/HepB). Further doses of polio-containing vaccines are given at the age of 3 years and 4 months as part of the pre-school booster (dTaP/IPV) and at around 14 years old (Td/IPV) as part of the teenage booster.

Reference

1. WHO (November 2024). ‘Poliovirus detections in European Region underscore importance of vaccination and vigilance’.