Poliomyelitis or polio is a viral infection that can cause permanent paralysis and death in those infected.¹ It commonly affects children under five years of age and may affect any individual who is not vaccinated against the virus.¹ In the 20th century, it was one of the most widespread and feared diseases as it killed or paralysed nearly half a million people annually around the mid-1950s.¹ Although the prevalence of polio has declined with the intervention of modern medicine, it is still important to understand the risks of traveling to countries where polio is still prevalent and take necessary precautions to mitigate them.

Let's dive in!

Transmission and symptoms

Poliomyelitis is caused by the poliovirus, which spreads through the consumption of food and water contaminated with fecal matter of a polio-infected individual.¹ It may spread through breathing droplets expelled via sneezing or coughing of a person infected with the virus, direct oral contact with an infected individual,¹ or by coming into contact with contaminated objects.¹ 

75-90% of people with polio show no symptoms of any infection but still can spread the disease through fecal-oral and oral-oral routes. This is known as subclinical or asymptomatic polio.¹ They do not require medical care.

Around 4-8% of infections result in abortive poliomyelitis, wherein infected individuals experience flu-like symptoms that subside within a week with supportive care.¹

Approximately 1% of infections lead to non-paralytic polio,¹ wherein individuals first experience flu-like symptoms and the following:

• stiffness or pain in the neck
• stiffness or pain in the arms and legs
• headaches

Only around 0.5-1% of infected individuals experience paralytic poliomyelitis,¹ where there is an initial period of flu-like symptoms followed by 

• muscle spasm and pain in the back
•  neck and limbs
• difficulty in breathing and swallowing
• eventual loss of muscle reflexes 

Some individuals recover from paralytic poliomyelitis, but generally, if movement of limbs does not resume within 12 months, there is lifelong disability. If the virus attacks muscles responsible for breathing or heart muscles, death is inevitable.¹

Who is at risk?

Polio generally affects children under the age of 5 years due to their lowered immunity, but it can also affect adults who are not vaccinated for polio. The Injected Polio Vaccine (IPV) and the Oral Polio Vaccine (OPV) are the main components of worldwide efforts to combat polio at an early age. The United Kingdom’s National Health Service recommends the 6-in-1 vaccine (for Diphtheria, Tetanus, Whooping cough, Polio, Hib, and Hepatitis B) for babies at 8, 12, and 16 weeks of age to prevent polio amongst other diseases.²

Adults vaccinated against polio in their childhood are protected from the disease, but may be at risk of contracting it due to:

• Lowered protection provided by the vaccine in older adults³
• Lowered immunity due to HIV/AIDS, cancer treatment, transplanted organs³
• Traveling to regions with active polio outbreaks³

Risks of Polio for travelers

People traveling to polio-endemic areas must be aware of the risks, even if they are vaccinated. Polio-endemic areas are those where the polio virus is still in circulation. As of 2024, Polio is endemic in only Afghanistan and Pakistan.⁴

As polio spreads primarily through the fecal-oral route, areas with poor sanitation and unsafe drinking water have an increased likelihood of contracting polio.

Polio-endemic areas also have low vaccination rates because of limited healthcare infrastructure or political conflict, thus allowing the virus to circulate uninhibited and infect unvaccinated individuals.

When people travel to densely populated areas, the risk of contracting polio increases due to close contact with infected individuals, especially children, and shared sanitation facilities.

In rare cases, oral polio vaccines (OPV) lead to vaccine-derived strains that can spread in under-immunised populations.⁵ Travelers in such regions are at risk if they are not fully vaccinated.

Individuals with weakened immune systems due to HIV/AIDS, cancer, or immunosuppressive therapy, or those who are incompletely vaccinated or pregnant while traveling to areas with active outbreaks, are highly susceptible.³

Vaccination recommendations for travelers

Poliomyelitis cannot be cured, it can only be prevented by the use of vaccines, of which there are two types:

Inactivated Poliovirus Vaccine (IPV)⁶ 

This contains inactivated or killed poliovirus, which, when injected, causes the body’s immune system to produce antibodies against the virus. These antibodies fight live virus if and when the body is exposed to them, thus protecting the individual from the disease.

IPV is highly effective in preventing paralytic polio and does not cause vaccine-associated paralytic polio (VAPP). However, it does not produce antibodies in the mucosal tissues of the gut, which is essential to prevent person-to-person transmission.

Oral Poliovirus Vaccine (OPV)⁶ 

This contains a weakened live virus, which, when administered orally, replicates in the body and induces an immune response, which helps prevent person-to-person transmission, thus providing herd immunity. OPV is simple to administer but can revert to a form that can spread in communities with low vaccination rates, leading to outbreaks of vaccine-derived poliovirus (VDPV). Rarely, it can cause Vaccine-Associated Paralytic Polio.

The WHO recommends that adults traveling to high-risk or polio endemic areas be vaccinated via booster doses to obtain protection against polio infection, even if they were previously vaccinated in their childhood, as adults who are not fully vaccinated or whose immunity has lowered over time are still susceptible.⁷ Vaccinated individuals act as a shield against the spread of the virus and therefore protect vulnerable populations, contributing to community-level herd immunity.⁶

The WHO recommends that travelers receive a dose of OPV or IPV at least 4 weeks before traveling and within 12 months of departure.⁷ Travelers to polio-infected areas who have not received any polio vaccine previously should complete a primary polio vaccination schedule before departure, generally consisting of three vaccine doses⁷ over several weeks.

For people who previously received only IPV, OPV should be preferentially given as the booster dose in areas with active outbreaks., OPV stimulates the production of antibodies in the mucosal tissues of the gastrointestinal tract, which is the primary site of poliovirus entry. By inducing mucosal immunity, OPV contributes to herd immunity, protecting even those who are not vaccinated. This is particularly important in endemic areas where polio is still circulating.⁶

This additional layer of protection helps prevent the virus from multiplying and spreading. In case of unavoidable last-minute travel, travelers who have not received a documented dose of polio vaccine within the previous 12 months should still receive one dose of OPV or IPV before departure.⁷

It is also important to note that in areas of low vaccination rates with OPV, vaccine-derived polio virus (VDPV)⁵ can spread, even amongst individuals who are vaccinated against polio. Therefore, the decision to use OPV as a booster vaccine should be made carefully, considering the risks of VDPV.

Medical considerations before traveling

It is important to consult your physician before traveling, so that:

• They can review your medical history, identify any contraindications or specific needs, and provide advice specific to your health status and travel plans
• They can address any concerns or questions you may have about vaccines and their potential side effects
• You can obtain your vaccination records, which are required in some countries⁷

Health and safety precautions

Travelers to polio-endemic areas should prioritise health safety measures to minimise the risk of infection. Some of these practices are:

• Ensuring vaccination against polio is up-to-date
• Drink only bottled, boiled or treated water and consume food that is thoroughly cooked and served hot. Avoid ice and raw or undercooked foods, especially seafood and street food 
• Wash hands frequently with soap and water, especially before eating or after using the bathroom. When soap and water are not available, use alcohol based sanitisers
• Avoid crowded spaces or areas with poor sanitation for a prolonged period
• Avoid close contact with anyone who is sick
• Avoid swimming or bathing in contaminated water sources like lakes and ponds in high-risk areas

Post-travel precautions after visiting polio-endemic areas

It is crucial to take steps to monitor your health and prevent the potential spread of poliovirus upon returning from a polio-endemic region. Some post-travel precautions are:

Monitoring for polio infection symptoms

It is important to remain vigilant about polio symptoms for around 4-6 weeks after returning from an endemic area. Fever, fatigue, muscle pain, and stiffness in the neck can be indicative of polio infection.

Inform your healthcare provider

It is important to inform your primary care provider of your travel history if you start showing signs of polio infection or symptoms of another communicable disease. If you have not been vaccinated, you can obtain post-exposure preventive medicine.

Healthcare providers may recommend testing stool or other samples to rule out poliovirus infection, especially if there are active outbreaks in the areas visited.

Quarantine and vaccination

If you exhibit symptoms suggestive of polio, practice self-isolation to minimise the risk of spreading the virus to others. Encourage family members and others in your household to get booster vaccines, especially if they are at higher risk.

Continue to wash hands thoroughly with soap and water, especially after using the restroom or before handling food. Avoid close contact with young children, immunocompromised individuals, or unvaccinated people until you confirm you are healthy.

Reporting to health authorities

If you experience polio-like symptoms, report them to your local public health authority. Early detection can help prevent potential outbreaks.

Summary

Traveling to polio-endemic areas can be safe when one knows the risks and takes extensive steps to protect their health. Adults, even those vaccinated in childhood, should prioritise their health by updating their polio vaccination status,³ adhering to strict hygiene practices, and avoiding high-risk exposures. Post-travel vigilance, including monitoring for symptoms and seeking medical attention if needed, is equally important to prevent the potential spread of the virus.

By taking these precautions, you protect yourself and contribute to global efforts to eradicate polio, ensuring a safer future for everyone. Responsible travel practices are essential in reducing the burden of this preventable disease and achieving the shared goal of a polio-free world.