Polio is caused by a virus that spreads easily from person to person. It usually spreads through contact with the poo of an infected person. For example, from not washing your hands properly and putting them in your mouth, or from contaminated food or water.

Discovery of Polio in London

Last week in London, polio was detected in sewage screened by the National Institute for Biological Standards and Control (NIBSC), which has been surveilling the disease for decades as part of an international commitment to the World Health Organization.

The latest screening and analysis indicates that this polio strain is derived from the oral polio vaccine (OPV) still used in some parts of the world. Some countries use live, non-infective, non-virulent polio virus for their inoculations, which can evolve to become infectious in some cases.

In the UK we have a safe and incredibly effective vaccine for polio, commonly referred to as IPV. This is administered as a jab by a trained medical professional. IPV is part of the standard childhood immunisation programme and, with all four doses, is 99-100% effective. There is no live virus in this vaccine.

Usually, the virus isn’t detected again but this time several closely-related viruses were found in sewage samples taken between February and May 2022. This could imply that the virus has evolved into what’s known as vaccine-derived poliovirus type 2 (VDPV2) – which can in rare cases cause serious illness in people who are not fully vaccinated.

The detection of positive isolates has continued and there is evidence that low levels of person-to-person transmission have occurred – thus far without paralysis detected.

Limiting Spread and Further Transmission of Polio

For this outbreak, the key steps are for public health teams to track down these cases in London to limit spread and stop further transmission, and for parents to be encouraged to check their children are vaccinated against polio. Vaccination is the best protection, but good hygiene measures are important too: polio is introduced into the body through the mouth and often from faeces (poo). Recent outbreaks of measles and mumps in Britain reveal how many children have not had their routine childhood jabs, and how complacency over vaccination has taken hold as memory of diseases such as whooping cough and tetanus fades.

While wild poliovirus is endemic in just Afghanistan and Pakistan, vaccine-derived polio cases are regularly identified in sub-Saharan Africa and other parts of the world. Contending with multiple infectious diseases at the same time is normal in most parts of the world. Cholera, plague, malaria and measles still circulate and cause illness and death, despite major global health efforts to support governments in managing them.

What is polio?

Polio is a life-threatening disease caused by the poliovirus.

Polio symptoms

  • High temperature
  • Extreme fatigue
  • Headaches
  • Vomiting
  • Neck stiffness
  • Muscle pain

In extreme cases polio can cause life-long paralysis, usually in the legs, although movement typically comes back within a few weeks or months. The Polio virus can be life-threatening if it paralyses the muscles needed for breathing.

It mainly affects children under the age of five, although it can also impact unvaccinated adults.