Polio Cases In Several Countries Have the Medical Community On Alert

Polio is a disease that the medical community has been struggling with for decades. According to the World Health Organization (WHO), it is highly contagious, caused by a virus that invades the nervous system, and can cause paralysis in a matter of hours. It is transmitted from person to person, mainly by the fecal-oral route or through contaminated food or water, and multiplies in the intestine.

Its symptoms are fever, tiredness, headache, vomiting, stiff neck, and pain in the limbs. According to WHO estimates , one in 200 infections produces irreversible paralysis, usually in the legs, and 5% to 10% of these cases die from paralysis of the respiratory muscles. The most vulnerable to it are those under five years of age.

To curb this disease, which puts the health of millions of people at risk, the Global Polio Eradication Initiative was created in 1988. Thanks to vaccination, “wild poliovirus cases have decreased by more than 99% since 1988, when there were an estimated 350,000 cases in more than 125 endemic countries, compared to 33 reported in 2018,” says the WHO.

The recent appearance of polio cases in countries where the virus was eradicated, such as the United States, has raised concerns about the possible spread of the disease. In this article, we will tell you what you should know about the subject.

The reappearance of polio

Throughout 2022, the presence of the polio virus has been confirmed in different parts of the world where it had disappeared. In March of this year, the WHO reported an outbreak of polio in Israel. The virus was confirmed in several children and in wastewater in the region. For the month of June, the polio virus was detected in sewage in London. For their part, the health authorities of the state of New York confirmed on July 21 the detection of a case of paralytic polio in Rockland County. A victim is a 20-year-old man. It was also reported that the presence of poliovirus in sewage in two counties north of New York City; Rockland County and Orange County. This would be the first case of polio present in the North American country since 2013.

How did the spread occur?

Wild poliovirus is currently circulating in Afghanistan and Pakistan. However, experts indicate that the cases indicated above are not products of wild polio, but rather derive from an oral vaccine that is used in some countries, according to information published in a report in the journal Nature.

The Pan American Health Organization explains that this oral polio vaccine contains live viruses that have been attenuated to remove the ability to produce paralysis. In vaccinated children, the attenuated viruses reproduce and can persist for up to six weeks in the intestines and then be shed into the environment.

The inconvenience with the oral vaccine occurs when there is a large group of people who are not vaccinated, since "in places where vaccination coverage against polio is low, these viruses can be transmitted on many occasions among unvaccinated children, or partially vaccinated. On very rare occasions, these multiple transmissions can cause the viruses to mutate or change their genetic characteristics, being able to recover their ability to produce paralysis.” PAHO says.

Also read: Food Waste, An Environmental Problem In Latin America

Neither the United States nor the United Kingdom uses this vaccine. They use an injectable containing the inactivated virus, which has the ability to prevent the virus from infecting the nervous system. Its disadvantage is that it is not as effective as the oral one in reducing viral shedding and stopping transmission.

As for the New York case, a report from the United States Centers for Disease Control and Prevention (CDC) says that "because the patient had not traveled internationally during the potential exposure, detection of VDPV2 in patient stool samples indicates a chain of transmission within the United States that originated with a person who received an oral polio vaccine (OPV) type 2 abroad.” It also adds that "comparisons of genome sequences have identified a link to type 2 vaccine-associated polioviruses recently detected in sewage in Israel and the UK."

This seems to indicate that the virus is circulating widely through distant but interconnected places.

Another factor influencing these cases is that during the COVID-19 pandemic, routine vaccination services were interrupted in many regions, leading to a decline in vaccine administration that has left various communities exposed. It is currently estimated that Rockland County has a polio vaccination rate of 60.34% and Orange County 58.68%, in contrast to the state average of 78.96%, among children under two years of age who have received 3 polio vaccinations.

“With polio circulating in our communities, there is simply nothing more essential than vaccinating our children to protect them from this virus, and if you are an unvaccinated or under-vaccinated adult, choose to get vaccinated now. Polio is completely preventable and its re-emergence should be a call to action for all of us,” said New York City Health Commissioner Dr. Ashwin Vasan.