After the first U.S. case of polio in a decade, Canadian doctors urged vaccination.

Canadian infectious disease experts are taking notice after U.S. officials reported last week that an unvaccinated American had been diagnosed with the country’s first case of polio in nearly a decade.

Health Canada hasn’t recorded a case of the virus in more than 25 years, but infectious disease experts say they always have “ears and eyes open for vaccine-preventable diseases like polio” that are spreading around the world. I keep moving elsewhere.

“Any imported infection is just a flight away,” said Dr. Vinita Dubey, associate medical officer of health at Toronto Public Health.

The polio vaccine is part of standard childhood shots, but Dubey said some parents are choosing not to vaccinate their children and the COVID-19 pandemic has delayed vaccination for others.

This is creating a new risk of vaccine-preventable diseases as people return to international travel after a two-year hiatus, he said. Global polio vaccination efforts were halted for part of that time, exacerbating the problem.

A case of polio triggers a public health response and is reportable under international health regulations. By the time a case of polio paralysis is diagnosed, many people are likely to have been infected.

That’s the fear in Rockland County, NY, where a patient was diagnosed with polio after suffering a stroke. Officials are holding vaccination clinics and asking health care providers to watch for more cases.

The poliovirus is highly contagious and usually causes no symptoms or mild symptoms such as low-grade fever, malaise, nausea, diarrhea and sore throat. Diseases are most common in infants and young children, but adults who are not fully immunized can also become ill. The virus attacks the nervous system, with one to five percent of infections causing meningitis and less than one percent causing paralysis.

The introduction of immunization programs in the 1950s significantly reduced polio cases in Canada, when 5,000 children had polio each year. The last case of wild poliovirus in Canada occurred in 1977, while cases linked to the oral vaccine continued until 1995.

Polio infection can occur from the spread of wild virus or from transmission of the virus after a child receives the oral polio vaccine, which Canada stopped giving in 1996 but continues to be used in many other countries.

With the oral vaccine, the virus passes through the body and is excreted in the stool. The virus then spreads easily, infecting the next person when it gets into their mouth from hands contaminated with faeces. The virus can also remain in the throat and spread through respiratory secretions. People who have been vaccinated can pick up and transmit the virus but usually don’t get sick.

Canada’s routine childhood vaccine schedule includes an injectable polio vaccine before age two and a booster between ages four and six. The injectable form of the vaccine is inactivated and the virus is not transmitted from person to person.

Wild poliovirus is still endemic in two countries, Afghanistan and Pakistan, but more than 30 countries reported vaccine-associated polio outbreaks in 2020.

With summer travel in full swing, experts say both adults and children should keep their routine immunizations up to date and check if they need additional vaccines for their destination.

“Vaccine hesitancy is another effect of the pandemic,” said Dr. Valerie Lamarre, an infectious disease pediatrician at Montreal’s Saint-Justin Hospital.

And while the polio case in the U.S. isn’t a threat to Canada, Lamare said that doesn’t mean it should be ignored.

“We’ll see these cases pop up from time to time. It just means, ‘Wake up people. Get your vaccines,'” he said. “These diseases are treatable.”

Michelle Ward is a pediatrician, associate professor and journalist in Ottawa.

– Michelle Ward, The Canadian Press