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Polio (Poliomyelitis)
Polio is an infectious disease caused by viruses that result in a range of symptoms. Other terms for polio include poliomyelitis and infantile paralysis. Symptoms can range from a flu-like infection to paralysis that can occur within a few hours.
The history of polio dates back about 6,000 years. Egyptian mummies have been found with withered and malformed limbs likely caused by polio infection. In 1789, the first description of polio was recorded, and in 1834, the first documented epidemic occurred on the island of St. Helena. In 1855, Dr. Guillaume Benjamin Amand Duchenne showed that polio involved the anterior horn cells of the spinal cord. Landsteiner and Popper discovered the virus in 1908. The Iron lung was developed in the late 1920s to help polio survivors with breathing. U.S. President Franklin D. Roosevelt (1882-1945) was one of the most famous people who had polio. The polio virus was first cultivated in tissue culture (1949), and in 1951, the three types of poliovirus were isolated and identified. In 1954, the first large-scale trial of Dr. Jonas Salk’s vaccine (dead virus vaccine) was administered, and in 1958, Dr. Albert Sabin’s vaccine (live attenuated virus) was administered as an oral vaccine. In 2000, the U.S. switched to using inactivated polio vaccine by injection. Other countries still may use the oral poliovirus vaccine. The World Health Organization is trying to eradicate polio worldwide and has seen a 99% decrease in polio infections. In 2014, Southeast Asia was declared polio-free, but some countries in Africa and the Middle East still have new infections due to areas that cannot be reached by vaccine workers. The WHO still believes that polio eradication, like smallpox, may happen in the near future.
What causes polio?
Polio is caused by small RNA viruses, members of the enterovirus group of the Picornavirus family. There are three types (types 1, 2, and 3) of polio viruses; type I is responsible for about 85% of all paralytic infections. These types are antigenically distinct strains of viruses, and infection or immunity to one type does not protect against the other two types, however, immunity is lifelong once established.
The viruses cause the destruction of spinal cord cells, specifically the anterior horn cells.
The Americas, Western Pacific, and Europe have been certified polio-free by the World Health Organization. Other areas have a low incidence of polio, but people in war zones where vaccinations have been interrupted are at risk. The greatest risk factor for polio is not being vaccinated. People with immunodeficiency, very young individuals, pregnant females, caregivers for polio patients, travelers to endemic areas, and lab personnel who work with live polioviruses are at increased risk for polio.
Polio only infects humans and spreads through person-to-person contact. The virus lives in the throat and intestines and is spread through contact with feces or droplets spread in a sneeze or cough. It can also be spread by contaminated food or fluids. A person can be infectious before they develop symptoms.
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What are the symptoms of polio?
The majority of polio infections show little or no symptoms. Those who do show symptoms can be placed into two groups: non-paralytic polio (minor) and paralytic polio (major).
Non-paralytic polio symptoms:
- Flu-like symptoms of fever, sore throat, headache, malaise, and muscle stiffness (neck, back)
- Skin rash resembling measles rash. These symptoms last about 10-20 days and resolve completely, termed nonparalytic polio.
Paralytic polio symptoms:
- Paralytic polio symptoms mimic nonparalytic symptoms for about a week before increasing in severity with muscle aches, spasms, loss of reflexes, and flaccid paralysis (limbs become floppy).
- Paralysis may occur quickly, within hours of infection.
- Paralysis may be on one side of the body. Breathing may become inhibited or nonfunctional, requiring assistance.
Post-polio syndrome describes symptoms that develop 30 to 40 years after acute polio illness. The cause is unknown and symptoms include muscle and joint pain, spinal changes (scoliosis, spondylosis), and nerve compression. Slowly progressive muscle weakness, fatigue, and cold intolerance may also occur.
Diagnosis of polio
A preliminary diagnosis of polio can be made by a physician based on the patient’s history and physical examination. A definitive diagnosis is done by cultivating the poliovirus from mucus, stool, and/or cerebrospinal fluid. Serological tests are available to detect antibodies against poliovirus.
What is the treatment for polio?
There is no cure for polio once the virus has infected a person. Early diagnosis and supportive treatments such as bed rest, pain control, nutrition, and physical therapy can help reduce long-term symptoms. Some patients may require extensive support and care, including assisted breathing, special diets, and splints or leg braces t prevent pain, spasms, and deformities. Improvement in symptoms varies from patient to patient and is not easily predictable.
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What is the prognosis for polio?
The prognosis for patients with polio depends on the extent of damage caused by the virus. Many patients have few or no symptoms and an excellent prognosis. However, when paralysis develops, especially with decreased ability to breathe or swallow, the prognosis worsens. Many patients with severe symptoms progress to lifelong disabilities or death.
