Spain reinforces itself in the face of polio outbreaks in other countries

• Outbreaks Polio unleashes fear in New York due to the risk of a new epidemic

• Emerging infections Polio virus detected in London sewage

Just a few days ago the

(CCAES) directed by Fernando Simón published an update on the risk of circulation in Spain of the polio virus as a result of polio cases that are occurring in other countries and the detection this summer of the virus in wastewater from cities that had been polio-free for more than two decades, such as New York or London.

The international alert for the

represents a significant change in trend in the long-awaited path towards the eradication of the disease, which had begun to be glimpsed in 2020 and which now has the entire international community in check again .

The CCAES recognizes in its new risk assessment that

but at the same time believes that "the current high level of immunity" of the Spanish population "would minimize the possibility of transmission and circulation of poliovirus in the population.

In addition, according to the agency, even if the virus were to circulate again, given "the high quality of the epidemiological surveillance system for poliomyelitis and the high standards of environmental sanitation and water treatment, this possible introduction would have a minimal impact, so the The risk associated with poliovirus in Spain is currently considered very low.

However, the Coordinating Center for Health Alerts and Emergencies has

,

, identify pockets of susceptible population and urge people who are going to travel to areas of risk of transmission of the polio virus to go to international vaccination centers before the trip, among other measures.

What is the risk of infection by the polio virus?

Poliomyelitis is caused by infection with poliovirus.

Although there are three types of this pathogen (PV1, PV2 and PV3), two of them are considered already eradicated and

.

Man is the only known reservoir of poliovirus and transmission occurs directly from person to person by the fecal-oral route or respiratory route through pharyngeal secretions, although it can also be transmitted indirectly through fecal contamination of water. and food.

More than 90% of infections are asymptomatic,

in 4-8% they cause discomfort, vomiting or headache and in less than 1% aseptic meningitis can occur and,

,

that It mainly affects the extremities but can also affect the respiratory muscles and cause death.

Since when have there been no cases of polio in Spain?

The

of poliomyelitis due to wild polio virus in Spain

.

After that date there have been four cases of paralytic poliomyelitis in Spain, but all associated with vaccine or vaccine-derived poliovirus.

In which countries are there still cases of polio?

Both Spain and the European Region of the World Health Organization have been certified as a polio-free region since 2002. As of 2020, only two countries in the world had active transmission of wild poliovirus: Pakistan and Afghanistan.

However,

in countries that had not reported any cases since at least 2016, such as

.

In the United Kingdom, the United States and Israel, they have detected the circulation of poliovirus derived from the vaccine in their wastewater.

Can vaccine-associated polio cases occur?

"In Spain, no live vaccine is being used that could cause a case of vaccinal polio. All the vaccines that are being used in Spain are inactivated and cannot cause contagion," explains

.

international cases of polio associated with vaccines are due

to the fact that "vaccines can be inactivated or live virus. In Spain, even The live virus oral vaccine was being used in 2004. This live virus vaccine has some advantages, that it generates a more complete response and also immunizes the environment of the vaccinated person, but it has the risk that in an environment in which there may be someone who is immunosuppressed, the person can get sick".

Castilla explains that "to avoid this risk in

and the injected vaccine, the inactivated one, was chosen, which is safer. However, in endemic countries or where the injected vaccine is very expensive, the oral vaccine is still used and that is what means that the vaccine virus of the oral vaccine can be detected in wastewater in some countries or, in its case, reach Spain"

All in all, in his opinion, these oral live virus vaccines "in principle should not be a big problem because these vaccines had been widely used until 2004 and there were not a large number of cases either, but it is true that, although rare, That possibility does exist."

Will it be necessary to revaccinate the population against the polio virus?

The CCAES does not consider in its risk assessment actions such as the one undertaken in the United Kingdom to urgently vaccinate all children between 1 and 9 years of age in the London metropolitan area.

"In our environment

because we have

and much higher than that of other countries in our same socioeconomic context, and this has been the case for many years," explains Amós García, President of the Spanish Society of Vaccinology.

Jesús Castilla, a member of the working group on Vaccination of the Spanish Society of Epidemiology, also does not believe that a revaccination or extra campaign is necessary to recruit the population: "Vaccination

and, in the case of people who come from conflict countries where there have been gaps in vaccination, try to recover them and incorporate them into our vaccination schedules," he says in relation to countries such as Pakistan, Afghanistan or Ukraine, among others.

Could the polio virus change and current vaccines no longer be effective?

"The operation

. Right now there are several types of polio virus circulating, but there is one clearly predominant and vaccines have a very clear impact on the type of virus of circulating polio", explains Amós García, president of the Spanish Society of Vaccinology.

Conforms to The Trust Project criteria

Know more

• Infectious diseases

• Vaccines