The poliovirus re-emergence: did concentrated efforts against COVID-19 open the door?

Dear Editor,

Poliomyelitis, also known as polio, is a disabling viral disease that has been infecting humans for hundreds of years. The wild poliovirus, a serotype of enterovirus C, a member of the Picornaviridae family, is the most common cause of polio. Polio results in influenza-like symptoms, including fever, sorethroat, headache, abdominal pain, vomiting and aching muscles. However, meningitis appears in 1–5 patients per 100 cases. The most severe symptom is paralysis, which occurs at a rate between 1 per 200 and 1 per 2000 cases, depending on the serotype and can lead to death. By 1979, polio had been eradicated in the USA. The Global Polio Eradication Initiative (GPEI) was established in 1988 when the World Health Assembly issued a resolution to end polio.¹ (see Fig. 1)

Fig. 1.

Number of cases of paralysis caused by each of the circulating vaccine-derived poliovirus. The red dotted line marks the beginning of the COVID-19 pandemic. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Wild poliovirus comes in three primary strains: type 1, 2, and 3. Type 2 and 3 have been eliminated. Type 1 still circulates.²

The eradication of poliovirus is due to vaccination. Two types of vaccines are used.³ The first is the inactivated polio vaccine (IPV), which since 2000 has become the only vaccine given in the US, and the oral polio vaccine (OPV), which is still used in some countries.⁴ The GPEI has praised the OPV for providing immunity in the intestines where the virus replicates and for playing a significant role in polio eradication. Despite its benefits, it has been associated with the spread of other forms of polio in communities with low level of immunization. The circulating vaccine-derived poliovirus (cVDPV) has three serotypes, cVDPV1, cVDPV2, and cVDPV3. Unlike IPV, OPV circulates for prolonged periods and can mutate. It may then infect poorly immunized populations, especially in areas with low sanitation, as the virus is excreted in stools. For example, in Yemen, where a war has torn the country since 2015, 30 cVDPV1 isolates have been detected in a single governorate.⁵ Furthemore, in August 2020, it was stated that cVDPVs are the only poliovirus types in Africa.⁶

In 2022 alone, a total of 223 cases of paralysis caused by circulating vaccine-derived poliovirus have been reported across the world; two hundred and twelve of those were caused by cVDPV2. Cases were reported in Ghana, Democratic Republic of Congo, Benin, Niger, Nigeria, Chad, Somalia, and Mozambique. In Mozambique alone, 63 environmental samples of cVDPVs and 2 paralysis cases were reported in June 2, 022.⁷ Almost simultaneously, a warning was issued as a case was diagnosed in New York, USA. The individual who was hospitalized with flaccid lower limb weakness,was immunocompetent but unvaccinated and had acquired the poliovirus, according to the report. The cVDPV2 serotype was later identified to be the causative agent by the CDC.⁸ Between August 10-17, 2022, 9 more cases of cVDPV2 and 26 more cases of cVDPV1 were diagnosed in the Democratic Republic of Congo, Yemen, and Mozambique, respectively.

Following these new cases, 33 million vaccine doses were administered in five southern African countries. In addition, five more rounds of vaccination are expected in 2023. With the support of the WHO, ten environmental surveillance sites have been established in affected countries.⁹

There are strong suggestions that the shift in focus during the COVID-19 pandemic, the restrictions put into place by the pandemic and the stress it has put on healthcare workers, has led to the current situation.

This might have caused an immunity gap, which then gave the opening for polio to re-emerge. The WHO reports that polio immunization was affected by COVID-19 in 2020. Outreach workers were not able to visit homes to immunize children, and parents could not bring their children to health facilities. An immunity gap may have developed during this pause.⁸

The poliovirus re-emergence should be a pivotal warning for health policymakers, healthcare workers, governments, and the general public to reconsider how infections and pandemics are dealt with. To eradicate polio once and for all, vaccinations should proceed regardless of the global state to prevent causing an immunization gap. Additionally, IPV should be encouraged more than OPV as the latter has caused the emergence of new forms of polio, notably in third-world countries like Yemen and Ghana. Furthermore, awareness should be raised by health policymakers and governments to educate the public about the disease and the importance of hygiene. These campaigns should be given the same importance as those created during COVID-19. Finally, philanthropy is needed to provide under-immunized communities with the means needed for hygiene.

Funding sources

None.

Author contributions

Nour Shaheen, Abdelrahman Mohamed, Abdelraouf Ramadan, Abdulqadir J. Nashwan: Manuscript writing and editing.

All authors read and approved the final manuscript.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Data availability

No data was used for the research described in the article.