Have you ever heard of polio? If you are living in a developed country, chances are you have not. But polio was once a dreaded disease that paralyzed and killed millions of people around the world, especially children under 5 years of age. In this blog post, we will explore what polio is, how it spreads, what its symptoms are, how it can be diagnosed, prevented and treated, and what the current status of polio eradication is.

What is polio?
Polio, short for poliomyelitis, is an infectious disease caused by a virus called poliovirus. It belongs to a group of diseases known as enteroviruses, which infect the gastrointestinal tract and can sometimes invade the nervous system. Polio has been around for a long time, dating back to ancient times. There are records of polio outbreaks in ancient Egypt, Greece and Rome. The disease was also called Heine-Medin disease or infantile paralysis because it mainly affected young children and caused muscle weakness and paralysis.

Polio became a major public health problem in the 20th century, when it caused large-scale epidemics in many countries. The disease reached its peak incidence in the United States in 1952, with 20,000 cases of paralytic poliomyelitis. In developing countries today polio remains a major cause of disability.

There are three types of poliovirus: type 1, type 2 and type 3. All three types can cause paralysis, but type 1 is the most common and virulent. Type 2 was eradicated in 1999 and type 3 was eradicated in 2020. As of 2022, only type 1 remains endemic in two countries: Pakistan and Afghanistan.

How does polio spread?
Polio is highly contagious and spreads mainly through person-to-person contact. The virus lives in the throat and intestines of infected people and can be transmitted through fecal-oral routes or oral-oral routes. This means that people can get infected by swallowing contaminated food or water, or by coming into contact with the saliva or feces of an infected person. The virus can also spread through respiratory droplets from coughs or sneezes.

People who are infected with polio can spread the virus for up to six weeks even if they do not show any symptoms. About 90% of people who are infected with polio do not develop any symptoms at all. This makes it harder to detect and stop the transmission of the virus.

What are the symptoms of polio?
Polio can cause different types of symptoms depending on whether it affects the central nervous system (CNS) or not. The CNS consists of the brain and spinal cord and controls most of the body's functions.

The two major types of polio are abortive polio and paralytic or nonparalytic polio. Abortive polio does not affect the CNS and usually causes mild flu-like symptoms such as sore throat, fever, headache, vomiting, weakness and fatigue. These symptoms tend to be temporary and the patient can make a full recovery within two weeks.

Paralytic or nonparalytic polio affects the CNS and can cause more serious complications. Nonparalytic polio causes inflammation of the membranes that cover the brain and spinal cord (meningitis), which can lead to symptoms such as headache, neck, back, abdominal and extremity pain, fever, vomiting, stomach pain, lethargy and irritability.

Paralytic polio causes damage to the nerve cells that control muscle movement (motor neurons), which can result in muscle weakness, loss of reflexes and paralysis. Paralysis usually affects the legs but can also affect the arms, trunk or face. In some cases, paralysis can affect the muscles that control breathing (respiratory muscles), which can be fatal. Paralysis can be temporary or permanent.

About one in 200 infections leads to irreversible paralysis. Among those paralyzed, 5–10% die when their breathing muscles become immobilized.


Some people who have had paralytic polio may develop a condition called post-polio syndrome (PPS) years or decades later. PPS is characterized by new or worsening muscle weakness, fatigue, pain and joint problems. The exact cause of PPS is not known, but it may be related to the aging of the nerve cells that survived the initial infection.

How is polio diagnosed?
Polio can be diagnosed by testing samples of throat washings, stool or spinal fluid for the presence of the virus. This can be done by culture or by polymerase chain reaction (PCR), which amplifies the genetic material of the virus. Another way to diagnose polio is by measuring the level of antibodies against the virus in the blood. Antibodies are proteins that the immune system produces to fight off infections. A high level of antibodies indicates a recent or past exposure to the virus.

How can polio be prevented?
The best way to prevent polio is by vaccination. There are two types of polio vaccines available: oral polio vaccine (OPV) and inactivated polio vaccine (IPV).

OPV is a live attenuated vaccine, which means it contains a weakened form of the virus that can stimulate immunity but cannot cause disease. OPV is given as drops in the mouth and can provide protection for both the individual and the community. OPV can prevent most cases of paralytic polio, but in rare cases it can revert to a virulent form and cause vaccine-associated paralytic poliomyelitis (VAPP) or circulating vaccine-derived poliovirus (cVDPV).

IPV is a killed vaccine, which means it contains an inactivated form of the virus that cannot cause disease but can still induce immunity. IPV is given as an injection in the arm or leg and can provide protection for the individual but not for the community. IPV can prevent all types of polio, but it cannot stop the transmission of the virus.


Both OPV and IPV are safe and effective, and both are used in different combinations worldwide, depending on local epidemiological and programmatic circumstances, to ensure the best possible protection to populations. Multiple doses of either vaccine are required for lifelong immunity.

Other ways to prevent polio include improving public sanitation, maintaining proper personal hygiene, avoiding contact with infected people or contaminated objects, and seeking medical attention if symptoms occur.

How is polio treated?
There is no cure for polio, only supportive care. The aim of treatment is to prevent or reduce the symptoms and complications of the disease. Treatment may include:

• Antibiotics to prevent secondary infections in weakened muscles.
• Analgesics to relieve pain and inflammation.
• Antispasmodics to relax muscle spasms.
• Ventilators to assist breathing if respiratory muscles are paralyzed.
• Physical therapy to maintain muscle function and prevent deformities.
• Occupational therapy to help with daily activities and self-care.
• Braces, corrective shoes and orthopedic surgery to correct limb deformities.
• A balanced and nutritious diet to support recovery and health.
• Bed rest to ease the symptoms associated with the condition.

What is the current status of polio eradication?
The world has made remarkable progress in eradicating polio since 1988, when the World Health Assembly adopted a resolution for the worldwide eradication of polio, marking the launch of the Global Polio Eradication Initiative (GPEI). The GPEI is a global partnership led by national governments, WHO, Rotary International, CDC, UNICEF, Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance. The GPEI has mobilized millions of health workers, volunteers, donors and partners to deliver polio vaccines to every child in every corner of the world.

As a result of these efforts, the incidence of polio worldwide has been reduced by 99%, from an estimated 350 000 cases in more than 125 endemic countries in 1988, to 6 reported cases in 2021. More than 19 million people who would otherwise have been paralyzed by polio are walking today. More than 1.5 million lives have been saved by preventing deaths from polio-related complications. The world stands on the threshold of eradicating a human disease globally for only the second time in history, after smallpox in 1980.

However, challenges remain. Polio still persists in two countries: Pakistan and Afghanistan. These countries face complex political and security situations that hamper access to children for vaccination. They also face social and cultural barriers that affect community acceptance and demand for immunization. Moreover, outbreaks of cVDPV continue to occur in under-immunized populations due to low routine immunization coverage and gaps in surveillance.

To overcome these challenges, the GPEI has developed a new strategy for 2022–2026 that aims to end all forms of poliovirus transmission and deliver a lasting legacy for global health. The strategy focuses on four main objectives:

• Interrupt transmission of all polioviruses by strengthening immunization systems and reaching every child with multiple doses of polio vaccine.
• Contain and certify poliovirus eradication by ensuring safe handling and destruction of poliovirus materials in laboratories and vaccine facilities.
• Integrate polio functions into health systems by transitioning the polio assets and infrastructure to support other health priorities and emergencies.
• Certify and celebrate a polio-free world by engaging communities, leaders and partners to recognize and sustain this historic achievement.

The success of the strategy depends on the commitment and collaboration of all stakeholders, including governments, donors, partners, health workers, communities and parents. Everyone has a role to play in making polio history and ensuring a healthier future for all children.

Conclusion
Polio is a devastating disease that can cause paralysis and death, but it can be prevented by vaccination. The world has made tremendous progress in eradicating polio, but the fight is not over yet. We need to keep up the momentum and finish the job. Together, we can end polio for good and create a lasting legacy for global health.