Poliomyelitis (Polio)

Overview

Poliomyelitis, or polio, is a contagious disease caused by the poliovirus. Most people who are infected have no symptoms or only a mild illness. In a small number of cases, the virus invades the nervous system and damages the nerves that control muscles, which can cause weakness or permanent paralysis. When the muscles used for breathing are affected, polio can be life-threatening.

Thanks to widespread vaccination, polio has been eliminated from most of the world and cases are now very rare. It remains a concern in a few regions and can re-emerge where vaccination rates fall. Polio cannot be cured once it occurs, which is why prevention through vaccination is so important.

Symptoms

Most poliovirus infections cause no symptoms. When symptoms occur, they vary widely:

• Mild (abortive) polio: Flu-like illness with fever, sore throat, headache, tiredness, nausea, and stomach pain that resolves within days.
• Non-paralytic polio: The above plus signs of irritation of the lining around the brain and spinal cord, such as stiff neck and back, and muscle pain.
• Paralytic polio: A rare but serious form causing muscle weakness or paralysis, often in the legs, sometimes affecting breathing or swallowing.

Sudden weakness or paralysis, difficulty breathing, or trouble swallowing are emergencies and require immediate medical care.

Causes

Polio is caused by the poliovirus, which spreads from person to person:

• Fecal-oral spread: The main route, through contact with the stool of an infected person, often via contaminated hands, food, or water.
• Respiratory droplets: The virus can also spread through droplets from coughs and sneezes.

After entering the body, the virus multiplies in the throat and intestines. In some people it enters the bloodstream and reaches the nervous system, where it can damage the nerve cells that control muscle movement, leading to paralysis.

Risk Factors

• Not being vaccinated against polio
• Living in or traveling to areas where polio still circulates
• Poor sanitation and limited access to clean water
• Young age, historically the group most affected
• Close contact with someone infected with the virus

Diagnosis

Polio is diagnosed based on symptoms, exposure history, and laboratory tests:

• Laboratory testing: The poliovirus can be detected in samples such as stool, throat secretions, or the fluid around the spinal cord.
• Clinical assessment: Reviewing symptoms such as acute muscle weakness and signs of nervous system involvement.
• Public health reporting: Suspected polio is a reportable condition so that outbreaks can be identified and controlled.

Treatment

There is no cure that eliminates the poliovirus, so treatment focuses on relieving symptoms and supporting the body:

• Supportive care: Rest, fluids, pain relief, and treatment of fever.
• Breathing support: If breathing muscles are affected, mechanical ventilation may be needed.
• Physical and occupational therapy: To maintain mobility, prevent deformities, and aid recovery of muscle function where possible.
• Long-term care: Braces, mobility aids, and ongoing rehabilitation for those with lasting weakness.

Some people who recover may develop new muscle weakness and fatigue years later, known as post-polio syndrome.

Prevention

• Vaccination is the most effective protection; complete the recommended polio vaccine schedule
• Ensure children receive all doses on time
• Get recommended booster doses before traveling to areas where polio still occurs
• Practice good hand hygiene and safe food and water handling
• Maintain good sanitation to limit fecal-oral spread

When to See a Doctor

See a doctor if you or your child has unexplained muscle weakness, especially after possible exposure or travel to an area where polio occurs. Seek emergency care immediately for:

• Sudden muscle weakness or paralysis
• Difficulty breathing
• Trouble swallowing
• Severe neck stiffness with fever and headache

If you are unsure whether you or your child is up to date on polio vaccination, ask your healthcare provider.

Related Topics

Frequently Asked Questions

References

1. Centers for Disease Control and Prevention (CDC). Polio.
2. World Health Organization (WHO). Poliomyelitis.
3. MedlinePlus, U.S. National Library of Medicine. Polio and post-polio syndrome.
4. National Institute of Neurological Disorders and Stroke (NINDS).