Poliomyelitis? Transmission, Risk Factors, Effects and prevention


Poliomyelitis, commonly called polio, is a highly infectious viral disease that affects nerves, leading to partial or full paralysis. There is no cure for poliomyelitis. The focus of modern treatment has been on providing speedy relief of symptoms and preventing complications.

Poliomyelitis (Polio) which is one of the highest disabling acute diseases in the world spreads from person to person. Primarily, it spreads through the fecal-oral contact. It is one of the most dreaded childhood diseases of the 20th century. Polio epidemics have crippled thousands of people, mostly young children of less than 15 years. Poliomyelitis has caused paralysis and death for much of human history. It had silently existed for thousands of years as an endemic pathogen.

Early detection, reporting and investigation help in planning for mass vaccination to prevent deformities, complications and deaths. Make good use of the information provided on Poliomyelitis. It’s important you know and comply with the preventive measures against Poliomyelitis. Therefore, we must emphasize that early vaccination, identification; and prompt medical management interrupt polio attack and spread.


Poliomyelitis is highly infectious disease transmitted by carrier or ingesting foods or drinks contaminated with poliovirus from fecal matters. The incubation period (time between first exposure and first symptoms) of poliovirus attack is 3-35 days. Within this period, the poliovirus can cause serious neurological illness with permanent partial paralysis. This is especially in children under 15 years if nerve cells controlling their muscles are affected during the attacked.

There are three immunologic types of poliomyelitis virus.  Exposure to one type produces immunity only to that type, so infection with the other types is still possible. Poliomyelitis Virus (PV) 1 is the most commonly encountered form that is associated with paralysis. The likelihood and extent of developing paralytic polio increase with age. Also, paralysis rate depends on the serotype of the infecting poliovirus. The highest rates of paralysis (one in 200) are associated with poliovirus type 1. For each case of paralysis caused by wild poliovirus, an estimated 200 to 3,000 other contagious asymptomatic carriers exist.

Humans are the only known reservoir of poliovirus, transmitted most frequently by persons with in- apparent infections. There is no asymptomatic carrier state except in immune deficient persons. Person-to-person spread of this highly contagious poliovirus is through the fecal-oral (intestinal) channel. This is the most common route of transmission, although the oral-oral (oropharyngeal) route may account for rare cases.

Poliovirus is enterovirus that predominantly infect gastrointestinal tract. This is through infected mucus or phlegm from the nose or mouth, or by contact with infected feces. The virus enters the mouth and nose, multiplies in the throat and intestinal tract. And it is absorbed and spread through the blood and lymph system. Poliovirus can survive and multiply within the blood and lymphatic cells for as long as 17 weeks. It causes sudden onset (acute infection) after a short incubation period and is highly infectious. The disease spreads through contamination within households and communities. Also, the spread is through contaminated water supplies if public hygiene and sanitation are inadequate.


Poliovirus infection typically peaks in the summer and fall. There is no seasonal pattern in tropical climates. In developing countries, acute poliomyelitis affects children and young adults who have not been vaccinated. The disease can be fatal if the respiratory muscles become paralyzed. Adults are more likely than children to develop paralytic polio. In areas where there is outbreak, those most likely to get the disease include children, pregnant women and the elderly. However, in endemic areas, wild polioviruses can infect virtually the entire human population, with fatal health implications.


Factors that increase the risk of poliomyelitis or affect the severity of the disease include:

  • Immune deficiency
  • Malnutrition
  • Tonsillectomy
  • Physical activity immediately following the onset of paralysis
  • Skeletal muscle injury due to injection of vaccines or therapeutic agents
  • Pregnancy


Possible Complications of poliomyelitis are:

  • Aspiration pneumonia, a form of heart failure found on the right side of the circulation system
  • Lack of movement
  • Lung problems
  • Myocarditis
  • Paralytic ileus (loss of intestinal function)
  • Permanent muscle paralysis, disability and deformity
  • Pulmonary edema
  • Shock
  • Urinary tract infections
  • Post-polio syndrome (occurs in some patients 30 or more years after their first polio infection).


Poliovirus can spread and replicate, destroying motor neurons within the spinal cord, brain stem or motor cortex. This leads to muscle weakness and acute flaccid paralysis. Brain or spinal cord involvement is medical emergency that may result to paralysis or death from respiratory problems. Disability is more common than death.  In most cases, the growth of the paralyzed leg is slowed while the other leg continues to grow normally. The result is that one leg is shorter than the other, causing the affected person to limp; and lean to one side. This posture leads to deformities of the spine (scoliosis), osteoporosis and increased likelihood of bone fractures. It is clear that paralysis makes some people to develop new functional restrictions. This affects activities of daily living and may compromise the capacity to manage independently. Development of paralytic polio (spinal, bulbar or bulbospinal) varies. This is based on amount of neuronal damage, inflammation that occurs and portion of the central nervous system affected.


Massive, global vaccination campaign against poliomyelitis since the past 20 years confines polio to few Africa and Asia countries. However, outbreaks can still occur in the developed world. This is predominantly among the unvaccinated or noncompliant to full vaccination schedule or campaign against poliomyelitis. Polio often attack unvaccinated persons who travel to areas where the disease is endemic.

Developed in the 1950s, polio vaccines have reduced the global number of polio cases per year. This is due to enhanced vaccination efforts led by Rotary International, the World Health Organization and UNICEF. Oral Polio Vaccine (OPV) is inexpensive, easy to administer and produces excellent immunity in the intestine. It helps to prevent wild poliovirus infection in endemic areas. It has been the vaccine of choice for controlling poliomyelitis in many countries.  Rarely (about one case per 750,000 vaccine recipients), the attenuated virus in OPV reverts into a form that can cause paralysis.  Most industrialized countries have switched to irreversible Inactivated Poliovirus Vaccine (IPV). This is used either solely or in combination with oral polio vaccine.


Three serotypes of poliovirus that cause subclinical, non-paralytic and paralytic infections have been identified. All three are extremely virulent and produce similar disease symptoms and signs. Approximately 90% of polio infections cause no symptoms at all.  Affected individuals can exhibit these range of symptoms and signs that last 2-15 days if the virus enters the blood stream. They include moderate fever (5 – 7 days before other symptoms) and malaise (general discomfort or uneasiness).  Observed are headache, sore throat, vomiting, diarrhea and fatigue (excessive tiredness). Muscle tenderness, stiffness and spasm in any area of the body are common. Reported are pains or stiffness of the back, arms, neck, legs (calf muscles) and abdomen, skin rash or lesion with pain.  Abnormal sensations (but not loss of sensation) in the body and bloated feeling in abdomen are common presentations.  Constipation, passing urine with difficulty, drooling and irritability or poor temper control are noticed.  Quick asymmetrical muscle weakness which worsen into paralysis, painful feeling even with mild touch and runny nose are other symptoms. There may be weak tinny limbs. Acute onset of flaccid paralysis in one or more limbs with weak, floppy and poorly controlled or absent tendon reflexes in the affected limbs are among. Confusion and changes in mental status, seizures and spastic paralysis are reported.  Absent or diminished sensation in paralyzed limbs, difficulty in breathing, speaking and swallowing causing suffocation, and heart problems are observed.  There may be facial weakness, double vision, difficulty in chewing, abnormal respiratory rate, respiratory arrest, pulmonary edema and fatal shock.


Ensure the recommended Oral Polio Vaccine (OPV) doses are completed on schedule.  OPV is over 90% effective in halting poliovirus infection and reducing the severity of the infection on patients. Report someone close to you who has developed poliomyelitis to healthcare providers. Avoid delays in reporting symptoms of polio especially, sudden onset of weakness of limb(s) to the nearest health facility within 14 days.  Dirty homes (poor hygiene) expose foods and drinks to contaminated feces; and infected throat and nose secretions should not be allowed. Movement of unvaccinated babies from polio endemic areas to polio free areas should be discouraged. This is good in reducing childhood exposure and boosting their immunity to the disease.  Poor sewage disposal, unclean water supplies and travel to areas with polio outbreak should be avoided.


Engage in moderate exercise as recommended by your physiotherapist and eat nutritious diet. Wear braces or corrective shoes on the affected limb(s) and use moist heat (heating pads or warm towels). They help to reduce muscle pain and spasms; and to recover muscle strength and function. Wear portable chest and abdomen ventilators to support breathing if in difficulty. Use hydrotherapy, electrotherapy, massage and passive motion exercises to relax the muscles of the affected limb(s).

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