Explainer: Why has polio been found in London, New York and Jerusalem, and how dangerous is it?

LONDON, Aug. 15 (Reuters) – Polio, a deadly disease that used to paralyze tens of thousands of children a year, is spreading for the first time in decades in London, New York and Jerusalem, prompting catch-up vaccination campaigns. read more

REQUESTED DISEASE

Polio terrified parents around the world in the first half of the 20th century. It mainly affects children under the age of five and is often asymptomatic, but can also cause symptoms such as fever and vomiting. About one in 200 infections leads to irreversible paralysis and of those patients up to 10% die.

There is no cure, but since a vaccine was found in the 1950s, polio has been completely preventable. Worldwide, the wild form of the disease has almost disappeared.

Afghanistan and Pakistan are now the only countries where the highly contagious disease, mainly spread through contact with faeces, remains endemic. But this year, imported cases were also found in Malawi and Mozambique, the first in those countries since the 1990s. read more

DIFFERENT TYPES OF

There are two main forms of polio virus. In addition to the wild-type described above, there are also rare cases of what is known as vaccine-derived polio.

It is this second form found in wastewater in the British capital of London and in New York in the United States, with one case of paralysis reported in New York State. Genetically similar virus has also been found in Jerusalem, Israel, and scientists are working to understand the link, according to the Global Polio Eradication Initiative (GPEI).

While vaccine-derived polio is almost unheard of in the aforementioned locations, it is a known – albeit rare – threat in other countries, causing outbreaks every year, including 415 cases in Nigeria in 2021.

It arises from the use of an oral polio vaccine that contains an attenuated live virus. After children are vaccinated, they excrete the virus in their feces for several weeks. In undervaccinated communities, this can then spread and mutate back into a harmful version of the virus.

While countries, including Britain and the United States, no longer use this live vaccine, others do — particularly to stop outbreaks — enabling global spread, especially as people began to travel again after COVID-19, it said. experts.

WHY NOW

But experts agree that the main driver behind both vaccine-derived and wild polio outbreaks remains undervaccinated populations, said Derek Ehrhardt, global polio lead at the United States Centers for Disease Control and Prevention (CDC).

Vaccine hesitation was a growing problem before the pandemic, after which COVID-19 caused the worst disruption to routine immunization in a generation, according to the United Nations. read more

In 2020, there were 1,081 cases of polio from vaccines, about three times as many as the year before. There had been 177 cases so far in 2022, following major efforts to get polio vaccination campaigns back on track.

But the wastewater findings are still a wake-up call for parents with one important message, according to scientists around the world, including David Heymann, epidemiologist at the London School of Hygiene and Tropical Medicine: Protect children by getting them vaccinated.

Reporting by Jennifer Rigby Editing by Mark Heinrich

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