Polio is an infectious disease caused by poliovirus (enterovirus). The virus is transmitted mainly by the fecal-oral route (through contaminated hands, water, food), less often by respiratory secretions. The source of infection is humans – a sick person or a carrier.
The incubation period (from infection to symptoms) is usually 7–10 days, but can reach 4–35 days.
Two of the three "wild" types of virus have already been eliminated worldwide: WPV2 (2015)** and WPV3 (2019) – WPV1 currently remains a problem.
Most at risk of illness and severe course are:
unvaccinated or incompletely vaccinated people,
especially children (in practice most often <5 years old),
people with reduced immunity.
2. Symptoms of polio
Most infections are asymptomatic or have mild symptoms. When symptoms appear, they may resemble a "flu-like" infection: fever, fatigue, headache, nausea/vomiting, sore throat, muscle pain.
In a small percentage of patients, the virus attacks the nervous system and can cause:
aseptic meningitis,
acute flaccid paralysis (sudden weakness/paralysis of limbs),
in severe cases, paralysis of respiratory muscles (life-threatening).
Urgent medical consultation / ER is necessary when the following appear:
sudden weakness or paralysis of a limb,
shortness of breath, problems with swallowing/speech,
severe headache with stiff neck, high fever, disturbances of consciousness.
3. Where does polio occur? (countries and areas)
"Wild" poliovirus type 1 (WPV1) still persists endemically in Afghanistan and Pakistan; WHO reports that WPV1 transmission remains geographically concentrated mainly in these two countries.
At the same time, poliovirus (including vaccine-derived – cVDPV) is detected/circulates periodically in various regions of the world. CDC publishes a current list of places where circulating poliovirus was detected in the last 12 months (the list varies and includes, among others, part of African and Asian countries, but also single detections in Europe).
This information is particularly important for:
people traveling to regions with poorer sanitary conditions,
people traveling long-term (work, volunteering, missions, stays >4 weeks),
families with children who do not have a full vaccination cycle.
4. How to protect yourself against polio?
A. General prevention
very thorough hand washing (especially after using the toilet and before eating),
safe water and food (especially during travel),
attention to hygiene when caring for small children (diapers, surfaces).
B. Vaccination (most important)
Type of vaccine: in Poland, the standard is the inactivated IPV vaccine (injection).
For whom recommended?
routinely for children (in Poland – mandatory vaccination),
for adults before traveling to places with increased risk of exposure to poliovirus,
for unvaccinated / incompletely vaccinated people – completing the schedule.
Vaccination schedule (Poland, children):
mandatory IPV vaccination: 2 doses in the 1st year of life, 1 dose in the 2nd year of life (16–18 months) and a booster dose in the 6th year of life (often in combined vaccines).
Schedule for adults (in travel practice):
if you were fully vaccinated in childhood: a single IPV booster dose is usually considered before traveling to a place with circulating poliovirus.
if vaccination is incomplete (1–2 doses) or no data: the IPV cycle should be completed before travel (doses at intervals of at least a few weeks – decision according to schedule and travel date).
Booster doses, "4 weeks–12 months requirement":
WHO indicates that in countries considered infected (WPV1/cVDPV with risk of international spread), residents and long-term visitors (>4 weeks) may need a polio dose given between 4 weeks and 12 months before international travel and an appropriate entry in the International Certificate of Vaccination or Prophylaxis (ICVP).
Duration of immunity – practically:
after a full cycle, immunity is long-lasting, but in travel, current status counts; with risk of exposure, a booster is most often used according to recommendations for travelers.
5. Summary
Polio is a disease that usually proceeds mildly or asymptomatically, but in rare cases can lead to permanent paralysis, respiratory failure, and death. It is particularly worth considering vaccination (or a booster dose) if you are traveling to countries with circulating poliovirus or going for a long term. It is safest to plan vaccination at least 4 weeks before departure, and with a stay >4 weeks in countries covered by WHO recommendations, remember about the 4 weeks–12 months window and entry in the ICVP.