The Ongoing Battle with Polio
Dianne Ankley, BSN RN, Immunization Nurse Educator, MDHHS Division of Immunization
There are three wild types of polio virus (types 1-3), which are naturally occurring and non-mutated strains. These three poliovirus serotypes have minimal heterotypic immunity between each other, so immunity to one does not produce significant immunity to the others. Poliovirus infects only humans, is most common in infants and young children, and is highly contagious. There is no cure for polio infection once you have it, but it is preventable through safe and effective vaccination.2
The spread of poliovirus occurs from person-to-person via the fecal-oral or oral-oral (sneeze or cough) routes. The virus enters through the mouth and multiplies in the oropharynx and gastrointestinal tract. The virus is usually present in nasopharyngeal secretions for 1 to 2 weeks and can be shed in stools for several weeks after infection, even in individuals with minor symptoms or no illness. The poliovirus incubation period for nonparalytic symptoms is 3 to 6 days. The onset of paralysis usually occurs 7 to 21 days after infection.2
Most people infected with poliovirus will not have any visible symptoms. About one out of four people will have flu-like symptoms that usually last 2 to 5 days, then go away on their own. Fewer than 1% of people will have weakness or paralysis in their arms, legs, or both. The paralysis can lead to permanent disability and death. 2
Inactivated polio vaccine (IPV) was first used in 1955. By 1962 though, a live attenuated polio vaccine (OPV) had replaced it boasting a longer lasting immunity, protection against the chain of transmission of the virus, and an easier method of administration (orally).1 Since 2000 though, only IPV has been authorized for use in the United States mainly due to cases of vaccine-derived poliovirus (VDPV).3
However, OPV still remains the workhorse of the global eradication program because it’s cheap, easy to use, and confers robust gut immunity that helps stop polio transmission. Unfortunately, where immunization rates are still low, the weakened strain of poliovirus from OPV can continue to spread from person to person and over time acquire enough mutations to become a VDPV and regain its ability to paralyze.1
Although polio was officially eradicated in the U.S. in 1979 (meaning no polio cases originating in the U.S.), the polio virus can still be brought into the country by travelers. In July 2022, CDC was notified of a case of polio in an unvaccinated immunocompetent adult individual from Rockland County, New York, caused by vaccine-derived poliovirus type 2 (VDPV2).3 The patient initially experienced fever, neck stiffness, gastrointestinal symptoms, and limb weakness. The patient was later hospitalized with flaccid lower limb weakness and was subsequently diagnosed with VDPV2. CDC confirmed the presence of poliovirus at several wastewater sampling sites in New York and is currently working with New York to test for poliovirus in wastewater samples.
Wastewater testing can provide information about where poliovirus might be circulating in a community in which a paralytic case has been identified; however, the most important public health actions remain ongoing case detection through national acute flaccid myelitis (AFM) surveillance and improving vaccination coverage in under vaccinated communities.5
The best way to protect everyone from polio is to maintain high immunity rates against poliovirus in the population through vaccination. Children should receive the childhood recommended schedule of one dose of IPV at 2 months, 4 months, 6-18 months, and 4-6 years. Use the catch-up schedule if the child is behind in their immunizations. Parents of children who will be traveling outside the U.S. should check with their provider or local health department about travel requirements.
For adults, the risk of contracting polio is extremely low because most have been vaccinated against it when receiving their childhood vaccinations. However, adults at increased risk of exposure who never received polio vaccination or have not completed their polio series should be vaccinated.6 Some of the situations that may put them at increased risk for exposure where they should talk with their healthcare provider to determine whether they may need additional poliovirus vaccination include:4
- Travelers who are going to countries where there is an increased risk of exposure to poliovirus.
- Laboratory and healthcare workers who handle specimens that might contain polioviruses.
- Healthcare workers or other caregivers who have close contact with a person who could be infected with poliovirus.
- Unvaccinated adults whose children will be receiving oral poliovirus vaccine (for example, international adoptees or refugees).
- Unvaccinated adults living or working in a community where poliovirus is circulating.4
Polio is a vaccine preventable disease, and we want to protect all Michiganders by making sure they are up to date with all recommended vaccines.
References:
1 Polio Timeline - Office of NIH History and Stetten Museum
2 Polio: For Healthcare Providers | CDC
3 Polio Vaccine: Vaccine-Derived Poliovirus | CDC
4 Adult Vaccination for Polio | CDC
5 Wastewater Testing and Detection of Poliovirus Type 2 Genetically Linked to Virus Isolated from a Paralytic Polio Case — New York, March 9–October 11, 2022 | MMWR (cdc.gov)
6 What Adults in the U.S. Should Know About Polio (cdc.gov)
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