Sunday, June 26, 2022

How dangerous is polio and how close is it to eradication?

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The discovery of traces of the poliovirus during routine testing of sewage at a north London sewage treatment plant has sparked an “urgent” investigation and provided an unwelcome reminder of a terrible disease many believed had been eradicated.

No cases of polio have yet been reported or confirmed in the UK, but if they were, they would be the first to be diagnosed in the UK in almost 40 years.

The US Centers for Disease Control and Prevention (CDC) describes polio, or poliomyelitis, as “a debilitating and life-threatening disease caused by the poliovirus [that] spreads from person to person and can infect a person’s spinal cord and cause paralysis.”

It mostly affects children under the age of five, but as the CDC points out, about 72 percent of those infected won’t experience any outward symptoms.

However, those who do suffer from a flu-like condition characterized by a sore throat, fever, fatigue, nausea, headache, and stomach pain that can last from two to 10 days.

In much rarer cases, more than one percent of cases, patients can develop a much more serious illness caused by the virus attacking the nerves in the spine and base of the brain, causing meningitis or paralysis and permanent disability can lead.

In even rarer cases, polio can prove fatal when the disease targets the muscles around the lungs, interfering with breathing.

The CDC warns that polio is “very contagious” and lives on in an infected person’s throat and intestines, allowing it to be transmitted through contact with their feces or through droplets from a cough or sneeze, with a patient being contagious for up to two weeks after becoming infected will.

There are two types of vaccines used to fight poliovirus: the inactivated poliovirus vaccine, which is the most common and is given by injection, and the oral poliovirus vaccine (OPV), which is given as a pill.

The former has been the only way given in the US and UK since 2000 and 2004 respectively – typically in infancy – but the OPV is still used elsewhere in the world.

What has caused such concern at the UK Health Security Agency about the samples of the disease recovered at London’s Beckon Sewage Works is that they indicate the “probable” spread of a vaccine-derived poliovirus type 2 (VDPV2) between eng interconnected people indicate surroundings.

VDPV2 is a rare, mutated form of the OPV-derived virus whose spread is impeding international efforts to eradicate polio forever.

The variant is typically found in underimmunized communities with poor sanitation, and as OPV has not been offered in the UK for 18 years, its occurrence is believed to be caused by infection from a person who has been vaccinated abroad.

The tracks were found at the facility in question between February and May 2022, which is worrying as the facility serves four million Londoners and although such samples are found annually, these particular examples appear to be related and share mutations, suggesting this that the virus is evolving.

The outbreak of the coronavirus pandemic in 2020 has also disrupted the delivery of polio vaccines to children, leading to a drop in uptake, meaning some children under the age of five are more vulnerable than usual, raising the possibility of an outbreak in one country considered has increased polio-free since 2003.

Vaccines have done a lot to stem the threat of polio worldwide since the World Health Assembly passed a resolution to eradicate it completely in 1988 and saw the number of “wild” cases fall by 99 percent from 350,000 this year to just 175 before Covid 2019, meaning that 18 million more people can now walk than would otherwise have been possible without intervention.

It is believed that the same initiative saved an estimated 1.5 million lives.

At the time the resolution was adopted, 125 countries were classified as endemic to polio, but in 2022 only two nations are: Afghanistan and Pakistan.

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