Polio is back, and Canada is not immune

In 2016, the world had only 37 cases of poliomyelitis, and the disease remained endemic in only two countries: Afghanistan and Pakistan. However, cases of infections and sewage samples in the United Kingdom, the United States and Israel are currently indicating an upsurge of the virus in these regions of the world and have prompted the authorities to launch vaccination campaigns.

Even in Canada, which has been polio-free for 20 years, medical experts see this upsurge in infections as a wake-up call. According to them, the virus still poses a threat to anyone who is not vaccinated, especially given the ability of polio to spread around the world via travelers and through sewage treatment systems.

On Wednesday, British public health announced it would offer a booster dose of the polio vaccine to children aged 1 to 9 in London, after finding the virus was spreading in several areas of the capital. Polio virus samples have been found in sewage from eight London boroughs. However, there are no confirmed cases of the disease.

The analysis carried out by the Health Security Agency of the United Kingdom nevertheless shows that the transmission has probably exceeded a close network of a few individuals. And we know that the areas of London where poliovirus is transmitted have some of the lowest vaccination ratessaid Dr. Vanessa Saliba, consultant epidemiologist for public health.

The agency said it is working closely with health authorities in the United States and Israel, as well as the World Health Organization (WHO), to investigate possible links between the polio viruses detected. in these two countries.

In July, Israel announced that a recent polio outbreak now appeared to be under control, after several people were infected, including a girl who now requires rehabilitation due to paralysis, according to the Jerusalem Post.

More recently, in New York State, an unvaccinated young adult suffered paralysis after infection with polio in Rockland County, an area known for low vaccination rates. It was the first reported case in the United States in nearly a decade.

Vaccination campaigns are underway, as samples of the virus have also been detected in sewage in Rockland and another county just north of New York. Hundreds of people could already be infected, according to public health officials.

Polio, one plane ride from Canada

Part of the challenge to eradicating poliomyelitis in the world actually comes from the vaccination approach used in some regions. While high-income countries now use an inactivated polio vaccine given by traditional injection, others rely on a weakened poliovirus that is easy to administer orally.

Both types of vaccine have helped curb the spread of the virus around the world and, importantly, neither can cause symptomatic infection in the person who receives it.

However, because the oral version finds its way into the stomachs of individuals who ingest it, it is flushed out of the body into sewage treatment systems, where over time the virus can revert to a form capable of causing sickness.

An Afghan health worker administers the polio vaccine on the outskirts of Jalalabad, Afghanistan, November 6, 2018.

Photo: Getty Images / NOORULLAH SHIRZADA

Under certain conditions, this can lead to a poliomyelitis epidemicconcedes Dr. Isaac Bogoch, infectious disease specialist at the University Health Network of Toronto. In fact, some parts of the world have experienced small outbreaks of vaccine-derived polio.

Laboratory tests carried out on the case in New York, for example, linked the virus samples to a person who had received the oral vaccine, which however has not been used in the United States since 2000. This suggests that the virus originated outside the United States, a place where [le vaccin oral] is administeredanalyzes public health.

In London, of more than 100 polio samples identified in sewage, most contained vaccine-derived viruses, according to the UK Health Security Agency, while others had enough mutations to more closely resemble so-called polio. savagewhich can have serious health effects.

International travel, between countries with high polio transmission rates and regions with lagging vaccination rates, could end up being a problem, said Wes Hazlitt, a polio survivor and president of the Post-Polio Network in Manitoba.

Poliomyelitis is just a plane ride away. »

A quote from Wes Hazlitt, President of the Post-Polio Network in Manitoba

Satisfactory but unequal vaccination coverage

So how at risk is Canada of experiencing a polio outbreak? It all depends on vaccination rates, many experts agree.

If there is a relaxation in the level of basic vaccines in children, i.e. measles, mumps, rubella, diphtheria, tetanus, whooping cough and poliomyelitis, then we risk seeing these diseases return.warns Dr. Anna Banerji, a pediatrician and infectious disease specialist in Toronto.

The vast majority of the Canadian population is vaccinated against polio. In children, the rate fluctuates. But the latest federal data, from 2017, shows that about 90 percent of toddlers have received all three required polio vaccines.

However, vaccination coverage is uneven across the country. In British Columbia and Manitoba, the polio vaccination rate is less than 90%. In Nunavut, it’s about 80%.

Consideration should also be given to the possible disruption of the administration of basic vaccines in children due to the closure of schools during the COVID-19 epidemic.

Certain pockets of the population could therefore be vulnerable to poliomyelitis, estimates Fatima Tokhmafshan, researcher and geneticist at the Research Institute of the McGill University Health Center, but according to her, Canadians should not worry too much about it.

If you see something going around, it’s good to be on your guard, but not to panic. […] Make sure those around you are vaccinated.

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