Polio is back: UK Public health officials declare a national incident after Poliovirus spreads for the first time since 1984

The last wild case of poliovirus was detected in 1984 and Britain was declared polio-free back in 2003.

If polio infects cells in the Central Nervous System, it can then replicate in motor neurons in the brain stem.

The UK Health and Security Agency (UKHSA) reported evidence of limited community transmission of poliovirus found in London’s wastewater.

Health officials warn that this is the first time that polio has spread in Britain for almost 40 years, urging people to make sure they have been vaccinated or boosted appropriately.

The transmission event was of a vaccine-derived poliovirus detected in sewage from North and East London in February and April. Experts suggest that a spread occurred between individuals.

Where did this poliovirus come from?

Health experts suspect the virus was imported from an individual who recently received an oral polio vaccine containing the live virus.

This was released via faeces and entered London’s sewers. After the eradication of polio, Britain began using an inactivated vaccine in 2004, which is not released in faeces.

This means that the vaccine-derived virus likely came from abroad.

Past detections occurred when individuals were vaccinated with the live oral polio vaccine (OPV) overseas before returning/travelling to the UK and shedding traces of vaccine-like polio in their faeces.

It is suspected this may have come from a country which uses oral vaccination programmes, for instance Pakistan, Afghanistan, or Nigeria.

Polio can be spread in multiple ways, including via poor hand hygiene or coughing and sneezing.

Why this case is worrying so many health officials:

It is not unusual for the vaccine-derived poliovirus to be detected each year in Britain’s sewage, however this case is different.

The latest virus has mutated and has since been classified as a ‘vaccine-derived’ poliovirus type 2 (VDPV2).

This behaves more like wild polio, the most commonly known poliovirus strain.

The virus multiplies in the intestines and those infected then release large quantities of it in their faeces for several weeks.

Common symptoms include a sore throat, fever, nausea, headaches, and stomach pain.

However, on rare occasions, this strain can compromise the spinal cord resulting in paralysis. If breathing muscles are affected this condition can become fatal.

Uptake of the Poliovirus vaccine in London:

Although children are regularly vaccinated for Poliovirus across Britain, health officials noted that the vaccine uptake in young people is lower in London.

Approximately 1 in 10 have not been vaccinated, with around 30% remaining unboosted in their teenage years.

Within unvaccinated populations, approximately 10% of polio infections can lead to paralysis.

Consultant Epidemiologist at UKHSA, Dr Vanessa Saliba, warned: “Vaccine-derived poliovirus has the potential to spread, particularly in communities where vaccine uptake is lower.

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

What are the next steps?

This is the first time that a polio strain has lingered in the system for a matter of months, the severity of the situation being that it suggests the virus may continue spreading and mutating.

In response, Chief Nurse for NHS London, Jane Clegg, said: “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 five in London who are not up-to-date with their polio vaccinations to invite them to get protected.”

For more information on polio and how to protect yourself you can consult the Centers for Disease Control and Prevention website.