What is polio, how does it spread, effects and prevention?


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

Poliomyelitis (Polio) which is one of the highest disabling diseases in the world is an acute, viral infectious disease spread from person to person, primarily 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 and had silently existed for thousands of years as an endemic pathogen.

Early detection, reporting and investigation help in future planning for mass vaccination to prevent deformities and complications that could result to death. 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 of polio, interrupt its attack and spread.


Poliomyelitis is a highly infectious disease caused by poliovirus which is transmitted by carrier or by ingesting foods or drinks contaminated by fecal matter from an infected person. The incubation period (time between first exposure and first symptoms) of poliovirus attack lasts for 6-20 days, with a maximum range of 3-35 days. Within this period, the poliovirus can cause serious neurological illness with permanent partial paralysis especially in children less than 15 years if nerve cells controlling 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 most closely associated with paralysis. The likelihood of developing paralytic polio increases with age, as does the extent of paralysis. 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 reported case of paralytic poliomyelitis caused by wild poliovirus, an estimated 200 to 3,000 other contagious asymptomatic carriers exist.

Humans are the only known reservoir of poliovirus, which is 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 through the fecal-oral (intestinal) channel is the most common route of transmission, although the oral-oral (oropharyngeal) route may account for rare cases.

The poliovirus is an enterovirus that predominantly causes infection of the gastrointestinal tract that is contaminated with infected mucus or phlegm 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 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 an illness of sudden onset (acute infection) after a short incubation period and is highly infectious. The disease spreads through contamination within households and more widely in the community 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 usually affects children and young adults who have not been vaccinated. The disease can be fatal if the muscles of respiration become paralyzed. Adults are more likely than children to develop paralytic polio. In areas where there is an 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 they are first infected).


Poliovirus can spread and replicate, destroying motor neurons within the spinal cord, brain stem or motor cortex leading to muscle weakness and acute flaccid paralysis. Brain or spinal cord involvement is a medical emergency that may result in paralysis or death (usually from respiratory problems). Disability is more common than death.  In most cases, the growth of the paralyzed leg is slowed by polio, 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 may lead to deformities of the spine (such as scoliosis), osteoporosis and increased likelihood of bone fractures. It is clear that the paralytic polio may cause some people to develop new functional restrictions that affect activities of daily living and may compromise their capacity to manage independently. This development of paralytic polio (spinal, bulbar or bulbospinal) varies only with the amount of neuronal damage and inflammation that occurs and the portion of the central nervous system affected.


As a result of massive, global vaccination campaign against poliomyelitis since the past 20 years, polio exists only in a few countries in Africa and Asia. However, outbreaks can still occur in the developed world, predominantly among people who have not been vaccinated or noncompliant to full vaccination schedule or campaign against poliomyelitis. Polio often attack unvaccinated persons who travel to an area where the disease is endemic.

Developed in the 1950s, polio vaccines have reduced the global number of polio cases per year from many hundreds of thousands to under a hundred today due to enhanced vaccination efforts led by Rotary International, the World Health Organization and UNICEF. Because Oral Polio Vaccine (OPV) is inexpensive, easy to administer and produces excellent immunity in the intestine (which helps to prevent wild poliovirus infection in endemic areas), it has been the vaccine of choice for controlling poliomyelitis in many countries. On very rare occasions (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), either as the sole vaccine against poliomyelitis 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. Although 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. The symptoms and signs include moderate fever (5 – 7 days before other symptoms), malaise (general discomfort or uneasiness), headache, red and sore throat, vomiting, diarrhea, fatigue (excessive tiredness), muscle tenderness, stiffness and spasm in any area of the body. Pain 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, irritability or poor temper control, asymmetrical muscle weakness which comes on quickly and may worsen into paralysis; painful feeling even with mild touch and runny nose are other symptoms and signs of polio. 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 that cannot be attributed to another apparent cause; confusion and changes in mental status, seizures and spastic paralysis.  Absent or diminished sensation in the paralyzed limbs, difficulty in breathing, speaking and swallowing which may cause suffocation and heart problems are observed.  There may be symptoms and signs of facial weakness, double vision, difficulty in chewing, abnormal respiratory rate which may lead to respiratory arrest and pulmonary edema; and shock which may be fatal.


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 who had contracted poliomyelitis. Report someone close to you who has developed poliomyelitis to healthcare providers.

People should avoid delays in reporting of symptoms and signs of poliomyelitis above especially, sudden onset of weakness of limbs to the nearest health facility or health professional within 14 days.  Dirty homes (poor hygiene) that can expose foods and drinks to contaminated feces; and infected throat and nose secretions from sneezing and coughing should not be allowed. Movement of unvaccinated babies from polio endemic areas to polio free areas should be discouraged, so as to reduce childhood exposure and boost their immunity to the disease.  Poor sewage disposal, unclean water supplies, traveling to an area that has experienced  polio outbreak without medical counseling and direct person-to-person contact that can expose you to poliovirus infection should be avoided.


Engage in moderate exercise as recommended by your physiotherapist and eat nutritious diet. Wear braces or corrective shoes on the affected limbs and use moist heat (heating pads or warm towels) 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 and use hydrotherapy, electrotherapy, massage and passive motion exercises to relax the muscles of the affected limb(s).

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