LONDON: Polio, a deadly disease that used to be used to kill tens of thousands of children every year, has been spreading in London, New York and Jerusalem for the first time in decades, spurring catch-up vaccination campaigns.
Polio scared parents around the world for the first half of the 20th century. It is mainly asymptomatic for children under five, but can also cause symptoms such as fever and vomiting. Around one in 200 infections leads to irreversible paralysis, and up to 10 per cent of those patients die.
There is no cure, but polio is completely preventable since a vaccine was found in the 1950s. The wild form of the disease has almost disappeared from the world.
Afghanistan and Pakistan are the only countries where the highly infectious disease remains endemic, mainly through contact with faecal matter. But this year imported cases were also found in Malawi and Mozambique, the first in those countries since the 1990s.
There are two main forms of polioviruses. Along with the wild-type outlined above, there are rare cases of vaccine-derived polio.
It is the second form detected in the water in the British capital, London, and in New York in the United States, with one case of paralysis reported in New York state. Scientists are working to understand the link, according to the Global Polio Eradication Initiative GPEI, and the genetically similar virus has also been found in Jerusalem, Israel.
While polio is almost unheard of in the above locations, it is a rare threat in other countries, causing outbreaks every year, including 415 cases in Nigeria in 2021.
It stems from the use of an oral polio vaccine containing weakened live virus. After children are vaccinated, they shed the virus in their faeces for a few weeks. This can then spread and mutate back into a harmful version of the virus in communities that are not well-vaccinated.
While some countries like Britain and the United States no longer use this live vaccine, others do it - especially to stop outbreaks - which allows for global spread, especially as people begin to travel again after COVID - 19, experts said.