Is polio returning? London’s sewer system is a concern for healthcare professionals

The United Kingdom is on high alert after the polio virus was found in its sewer system. Public health officials in the country are now calling for anyone who is not fully immunized to be vaccinated immediately.

The World Health Organization said it had confirmed that “vaccine-produced poliovirus type 2” had been found in environmental samples in London. As The Wall Street Journal explained, it is “a mutated form of the attenuated live virus found in the oral polio vaccine, which is still used in some countries.” People who receive the oral vaccine pass small amounts of the virus in their faeces. In places where adequate sanitation is lacking, it sometimes mutates to resemble the naturally occurring virus and can infect people who are not fully immune.

UK health officials say they have not identified any cases of polio, although wastewater samples show a local spread of the virus.

The UK’s Health Security Agency issued a press release Wednesday announcing the opening and launch of an investigation. In it, Dr. Vanessa Saliba, the agency’s epidemiologist consultant, said vaccine-derived poliovirus is rare and the risk to society as a whole is extremely low. But she noted that the virus has the potential to spread, especially in areas where vaccine levels are lower. Those who are vaccinated should not worry, but others should receive the vaccine, she said.

The Wall Street Journal reports that “the detection of polio in the West is very rare and is the last obstacle to the global impetus to eradicate the disease, which mainly affects children and in rare, severe cases can cause paralysis. Global health organizations say polio eradication is within reach, but that task has been thwarted by the re-emergence of the virus in countries where authorities believed it had been defeated.

The last case found in the UK was in 1984. The World Health Organization declared the United Kingdom polio-free in 2003. The United States received this designation after its last case in 1979.

Although largely eradicated worldwide, The Washington Post notes that polio remains endemic in Afghanistan and Pakistan.

About polio

Polio – its full name is polio – is a highly contagious virus that is spread through contact with the feces and, less commonly, the respiratory secretions of an infected person. It lives in the digestive system and throat and attacks the central nervous system. The most endangered are children under 5 years.

The Centers for Disease Control and Prevention says 72% of those infected will have no symptoms, while 1 in 4 will have flu-like symptoms, including sore throat, fever, fatigue, nausea, headache and stomach pain. The symptoms usually go away on their own.

Between 1 and 5 in 1,000 of those infected develop more serious symptoms that affect the brain and spinal cord. These symptoms may include:

  • Paresthesia, which is a feeling of pins in the legs.
  • Meningitis, an infection of the lining of the spine and / or brain.
  • Paralysis that can lead to permanent disability. If the paralysis affects the muscles used to breathe, 2% -10% of people who develop paralysis die.

Children who appear to be fully recovering sometimes experience new muscle pain, weakness, or paralysis 15 to 40 years later. This is called post-polio syndrome.

Infected individuals can spread the poliovirus immediately before and up to two weeks after noticing symptoms. Those without symptoms can also spread it. The virus can live in the feces of an infected person for many weeks, and without proper hygiene, the infection can spread to unvaccinated people, according to health experts.


In the early 1950s, polio outbreaks caused more than 15,000 cases of paralysis each year, according to the CDC.

The first polio vaccine was developed in 1956. Today, the polio vaccine is considered to be 99% -100% effective against the virus.

The most common form of polio is called wild polio, but the BBC explains that there is a rarer type associated with the oral form of the vaccine, which is suspected of opening London’s sewers.

The BBC says the oral vaccine provides excellent protection against wild polio, is easy to use and has been deployed in many parts of the world, keeping millions safe. “However, it contains a weakened, living form of the virus that can reproduce harmlessly in the gut. But this means that part of it is then excreted in the stool. In rare cases, this weakened form can spread to unvaccinated people. Over a long period of time, the virus derived from the vaccine can change to become more like wild polio. “

This is one of the reasons why many industrialized countries are now using the newer vaccine to kill the virus. Both are safe and effective, the article said.

Several countries, including Afghanistan, Pakistan and Nigeria, continue to use the oral vaccine. And the risk is small.

The BBC reports that in the last decade, with more than 10 billion doses of oral polio vaccine administered, outbreaks of polio virus-derived vaccines have led to less than 800 cases.

“During the same period, in the absence of vaccination with oral polio vaccine, more than 6.5 million children would be paralyzed by wild poliovirus,” the article said.

How polio is found in the sewers

UK officials said routine sewage surveillance there detected the virus several times a year, but this spring officials found the virus in several samples collected in London.

“Genetic analysis suggests that the samples have a common origin, most likely a person who traveled to the country around the new year,” The New York Times reported, citing Dr. Shahin Husseinov, a technical health official at the World Health Organization. “The last four samples collected appear to have evolved from this initial introduction, probably in unvaccinated children.”

As employees try to identify the source of the virus, it will not be easy: the area that directs waste to the plant includes 4 million people.

Stop the spread

The Global Polio Laboratory Network said it was important for all countries, but especially those with many trips and contacts with polio-infected countries, to “step up surveillance to quickly detect any new virus imports and facilitate a quick response.”

The United Kingdom has said it plans to get parents of young children vaccinated if they have not already. The World Health Organization says the polio vaccination rate in London is close to 87%.

Such a small outbreak could be in an extended family, virologist Angela Rasmussen of the University of Saskatchewan in Canada told NPR.

She said the COVID-19 pandemic had increased the number of people not vaccinated. In 2016, there were several dozen cases of polio in four countries, but in 2019-2020 the cases almost tripled. This led to more than a dozen known cases, spread in 30 countries, NPR reported.

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