Infantile paralysis

Alternative names
Polio; Poliomyelitis

Poliomyelitis is a disorder caused by a viral infection (poliovirus) that can affect the whole body, including muscles and nerves. Severe cases may cause permanent paralysis or death.

Causes, incidence, and risk factors

Poliomyelitis is a communicable disease caused by infection with the poliovirus. Transmission of the virus occurs by direct person-to-person contact, by contact with infected secretions from the nose or mouth, or by contact with infected feces.

The virus enters through the mouth and nose, multiplies in the throat and intestinal tract, and then is absorbed and spread through the blood and lymph system. Incubation (the time from being infected with the virus to developing symtoms of disease) ranges from 5 to 35 days (average 7 to 14 days).

Risks include:

  • lack of immunization against polio  
  • travel to an area that has experienced a polio outbreak  
  • pregnancy; very old or very young age  
  • trauma to the mouth/nose/throat, such as recent tonsillectomy or dental surgery  
  • unusual stress or physical exertion after an exposure to poliovirus (emotional and physical stress can weaken the immune system)

Polio occurs worldwide. However, no cases of polio have been reported in the United States in recent years. (The last case of non-vaccine related polio acquired in the United States was in 1979.)

There have been very few cases in the Western hemisphere. It once affected mostly infants and children, but now is mostly seen in people over 15 years old. It is more common in the summer and fall. Adults and young girls are more likely to be infected, but infection in young boys is more likely to result in paralysis.

Between 1840 and the 1950s, polio was a worldwide epidemic. Since the development of polio vaccines, the incidence is much reduced. Outbreaks still occur, usually in non-immunized groups.


There are three basic patterns of polio infection: subclinical infections, nonparalytic, and paralytic. Approximately 95% of these are subclinical infections, which may go unnoticed.

Clinical poliomyelitis affects the central nervous system (brain and spinal cord) and is divided into nonparalytic and paralytic forms. It may occur after recovery from a subclinical infection.


  • no symptoms, or symptoms lasting 72 hours or less  
  • slight fever  
  • headache  
  • general discomfort or uneasiness (malaise)  
  • sore throat  
  • red throat  
  • vomiting


  • symptoms last 1 to 2 weeks  
  • moderate fever  
  • headache  
  • vomiting  
  • diarrhea  
  • excessive tiredness, fatigue  
  • irritability  
  • pain or stiffness of the back, arms, legs, abdomen  
  • muscle tenderness and spasm in any area of the body  
  • neck pain and stiffness  
  • pain front part of neck  
  • back pain or backache  
  • leg pain (calf muscles)  
  • skin rash or lesion with pain  
  • muscle stiffness


  • fever, occurring 5 to 7 days before other symptoms  
  • headache  
  • stiff neck and back  
  • muscle weakness, asymmetrical (only on one side or worse on one side)       o rapid onset       o progresses to paralysis       o location depends on where the spinal cord is affected  
  • abnormal sensations (but not loss of sensation) of an area  
  • sensitivity to touch, mild touch may be painful  
  • difficulty beginning to urinate  
  • constipation  
  • bloated feeling of abdomen  
  • swallowing difficulty  
  • muscle pain  
  • muscle contractions or muscle spasms, particularly in the calf, neck, or back  
  • drooling  
  • breathing difficulty  
  • irritability or poor temper control  
  • positive Babinski’s reflex

Signs and tests

Examination may shows signs of meningeal irritation (similar to meningitis), such as stiff neck or back stiffness with difficulty bending the neck. When sitting, the person may need to support the body with the arms.

The person may have difficulty lifting the head or lifting the legs from a supine position (lying flat on the back). Reflexes may be abnormal. The disorder may resemble encephalitis, and it may affect the cranial nerves and cause difficulty with facial expression, swallowing, chewing, and so on. It may also cause choking or difficulty breathing.

Viral cultures of throat washings, stools, or cerebrospinal fluid (CSF) confirm the diagnosis (see CSF collection). Routine CSF examination may be normal or show slight increase in pressure, protein, and white blood cells.


The goal of treatment is to control symptoms while the infection runs its course.

Lifesaving measures, particularly assistance with breathing, may be necessary in severe cases.

Symptoms are treated according to their presence and severity. Antibiotics may be used to treat urinary tract infections. Medications, such as bethanechol, may reduce urinary retention. Pain killers are used to reduce headache, muscle pain, and spasms. Narcotics are not usually given because they increase the risk of breathing difficulty.

Moist heat (heating pads, warm towels, etc.) may reduce muscle pain and spasm.

Activity is limited only by the extent of discomfort and the extent of muscle weakness. Physical therapy, braces or corrective shoes, orthopedic surgery, or similar interventions may eventually be necessary to maximize recovery of muscle strength and function.

Expectations (prognosis)

The outcome varies with the form (subclinical, nonparalytic, or paralytic) and the site affected. If the spinal cord and brain are not affected, which is the case over 90% of the time, complete recovery is likely.

Brain or spinal cord involvement is a medical emergency that may result in paralysis or death (usually from respiratory difficulties).

Disability is more common than death. Lesions high in the spinal cord or in the brain are associated with greater risk for respiratory difficulty.


  • spread of infection to other non-immunized persons  
  • permanent muscle paralysis, disability, deformity  
  • pulmonary edema  
  • shock  
  • complications of immobility and respiratory (lung) involvement  
  • aspiration pneumonia  
  • high blood pressure  
  • urinary tract infections  
  • kidney stones  
  • paralytic ileus (loss of intestinal functioning)  
  • myocarditis  
  • cor pulmonale

Calling your health care provider

Call your health care provider if symptoms of poliomyelitis occur.

Call your health care provider if someone close to you has developed poliomyelitis and you are not immunized against the disorder.

Call your health care provider if your child’s polio immunization (vaccine) is not up-to-date.


Polio immunization (vaccine) effectively prevents poliomyelitis in most people (immunization is over 90% effective).

Johns Hopkins patient information

Last revised: December 7, 2012
by Sharon M. Smith, M.D.

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