The discovery was made in the northern and eastern parts of the city, thanks to the routine monitoring of London’s wastewater. According to UK Health Security Agency the extent of the spread of infection must now be examined immediately.
The disease polio, which can cause severe paralysis, was common during the first half of the 20th century. Thanks to vaccines, it is today almost completely eradicated. The most recent Swedish case was registered in 1977.
But ironically the disease can also occur due to the vaccination. Helene Norder, adjunct professor at the University of Gothenburg and expert on both polio and virus in wastewater, explains:
– There are three wild types of polio: type 1, 2 and 3. The 2nd and 3rd are extinct, while type 1 is still found in Afghanistan and northern Pakistan. But the vaccine used to fight polio in large parts of the world consists of a live vaccine that is genetically modified so that it does not cause the disease, she says.
The advantage is that the vaccine can be easily distributed. A drop on the tongue is all that is needed for antibodies to develop in the gut. The vaccine then passes out with the faeces, which in the long run can lead to the spread of immunity, if others come into contact with the faeces of a vaccinated person, if he or she has not washed his or her hands properly.
– But there is an obvious disadvantage, because when the vaccine has passed the intestine ten to 15 times, it begins to change so that it goes back to the wild type that causes disease, says Helene Norder.
This virus is called “Vaccine derived polio virus” and it is such an altered vaccine virus that has now been found in London. What worries the authorities is that the discovery was made in several measurements in a row, which indicates that there is one or more people who secrete the virus constantly and that this virus, which may develop into a variant that causes polio, is circulating among humans.
In Sweden, the oral vaccine has never been used. In the 1950s, Sweden went its own way when the Swedish Bacteriological Laboratory developed a vaccine based on killed virus. However, such a vaccine has the disadvantage that it must be given with syringes and in several doses.
For three years now, the WHO has been recommending the use of the killed vaccine. This week it was 20 years ago the organization declared Europe free from polio.
Facts. Also called polio
Polio, also known as polio, is caused by an enterovirus.
The disease can go unnoticed, but about ten percent of those infected get fever, headaches, nausea and vomiting. In one percent of the infected people, however, the symptoms can within a few days be followed by paralysis in both arms and legs as well as the respiratory muscles. One in 200 infected people gets a permanent paralysis. If the respiratory muscles are affected, the risk of fatal outcome is high.
During the first half of the 20th century, polio was a very common disease in Sweden. Outbreaks occur annually, but in some years the number of cases could increase several times. The last epidemic in Sweden was in 1953, when more than 5,000 cases were registered, of which just over 3,000 cases were paralytic polio (polio with paralysis).
Protection against polio is included in the childhood vaccination program and the proportion vaccinated in Sweden exceeds 98 percent.
Source: Swedish Public Health Agency
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