What is polio?

Poliomyelitis, otherwise known as polio, is a contagious viral disease, mainly affecting children. Though cases are now rare, it can cause paralysis, breathing difficulties and even death.

In the past, polio was found worldwide. In the early 20th century, it became a major public health concern after repeated outbreaks affected millions of people worldwide.

After polio vaccines were developed and approved for use in 1955 (Salk vaccine) and 1962 (Sabin vaccine), the incidence of polio went down drastically in vaccinating countries. The last infectious polio case in the United States was in 1979. A global polio eradication program brought down the global incidence of polio from 350,000 cases per year in 1988 to only 416 in 2013. [1]

Today, polio is found only in a few countries and is mostly considered a 'disease of the past'. However, the number of cases in these countries has been slowly growing. Public health organisations aim to eradicate the disease completely in the near future and are currently concentrating on the countries where the polio virus is still found, namely Pakistan, Afghanistan, Nigeria, Syria and Somalia.

People who have had polio in the past can experience 'post-polio syndrome' later on in life.

Paralysis

An inability to move or feel; a loss of muscle function or sensation.

Vaccine

A preparation containing a microorganism (that causes a specific disease) in a dead or weakened state, or parts of it, for the purpose of inducing immunity in a person to that microorganism.

Viral

Pertaining to an illness caused by a virus.

1. Poliomyelitis (polio). World Health Organisation. Accessed 22 July 2014 from

External link

Causes

The cause of polio is the polio virus, which can reside in the human digestive system. It spreads from person to person via accidental contact with human stools (faeces). In a minority of cases, the virus enters the body's nervous system, causing nervous system symptoms.

Nervous system

The extensive network of cells and structures that is responsible for activating and coordinating the body's functions, sensory input and cognition.

1. Poliomyelitis (polio). World Health Organisation. Accessed 22 July 2014 from

External link

Risk factors

Anyone can contract polio, but it mainly affects children. You are at increased danger of being infected with the virus if you are:

  • A child under five years of age (80%-90% of cases); [2]
  • Living or travelling to a country where the virus is found;
  • Pregnant, or;
  • Suffering from a condition that weakens your immune system.

Immune system

The organs and cells involved in protecting the body against infection.

2. Poliomyelitis. Department of Health Victoria Australia. Accessed 23 July 2014 from

External link

Types and prognosis

Infection with the polio virus can have several outcomes:

  • Most people infected with the polio virus do not get ill and suffer no symptoms;
  • A minority of people experience mild symptoms ('abortive polio');
  • In a small minority of people, the virus enters the central nervous system and causes more pronounced nervous system symptoms ('non-paralytic polio'), and;
  • One to two in 1000 people infected with the virus will develop paralysis, which may be life-threatening ('paralytic polio'). [3]

Abortive polio

In 8-24% of infected people [3] , the virus causes mild symptoms that resemble many other viral illnesses, such as the flu. These can include:

  • Fever;
  • Headache;
  • Stiff muscles;
  • Sore throat;
  • Constipation;
  • Nausea, vomiting, and;
  • Fatigue.

These symptoms go away naturally after a few days.

Non-paralytic polio

In 1-3% of infected people, the virus causes the mild symptoms as for abortive polio, but then enters the central nervous system and causes inflammation there. [3]   At this stage, the muscles, neck and back can become stiff and painful.

The symptoms of non-paralytic polio go away naturally after a week or two.

Paralytic polio

A serious complication of non-paralytic polio that can appear in 0.1-0.2% of people infected with the virus. [3]  The polio virus enters the central nervous system as above, but then begins infecting and destroying nerve cells. This can cause paralysis of the muscles, leading to:

  • Severe muscle weakness;
  • Weak, strained breathing;
  • Severe constipation;
  • Drooling, and;
  • Loss of function in the limbs (most often the legs).

The more serious subtypes of paralytic polio can cause severe difficulties in breathing, speaking and swallowing. Those affected may need artificial ventilation in order to breathe.

Symptoms of paralytic polio can include trouble speaking and swallowing, constipation, trouble breathing and weak limbs.Paralytic polio can cause severe muscle weakening, fatigue and loss of limb function. 

Central nervous system

The part of the body's nervous system that includes the brain and the spinal cord.

Nervous system

The extensive network of cells and structures that is responsible for activating and coordinating the body's functions, sensory input and cognition.

Paralysis

An inability to move or feel; a loss of muscle function or sensation.

Viral

Pertaining to an illness caused by a virus.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

Methods for diagnosis

If your doctor suspects polio, they will look at your medical history, vaccination status and travel history. A throat swab and/or a sample of your faeces may be examined for the presence of the virus. A sample of fluid from around the spinal cord and brain may be taken by lumbar puncture, to detect the presence of virus in the nervous system.

Nervous system

The extensive network of cells and structures that is responsible for activating and coordinating the body's functions, sensory input and cognition.

Lumbar puncture

A procedure that uses a needle to collect a sample of cerebrospinal fluid, which is the clear fluid surrounding the brain and spine, from the lower back (lumbar region) for analysis. It can also be performed to remove any excess fluid or to deliver medications.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

Types of treatment

Polio cannot be cured; treatment focuses on easing the symptoms. Treatment can include:

  • Pain-relief medications, such as paracetamol or ibuprofen;
  • Heating pads to relieve muscle pain;
  • Physical therapy, massage, gentle exercise, and;
  • Mechanical breathing aids (usually portable ventilators) for those who have breathing problems.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

Potential complications

Post-polio syndrome

People who have had polio in the past can, decades later, experience post-polio syndrome (PPS). It is not yet clear why this happens, but may be connected with deterioration of damaged neurons in the spinal cord.

It has been shown that the polio virus is not present in PPS cases and people with PPS are not infectious.

Symptoms of post-polio syndrome can include:

  • Muscle weakness and fatigue;
  • Muscle and joint pain, and;
  • Breathing, sleeping and swallowing problems.

PPS usually develops gradually. It is not life-threatening, but can have a significant effect on your quality of life. As a general rule, people who have had a more serious polio illness are more likely to experience PPS.

PPS cannot be cured, but can be managed by:

  • Avoiding physical exertion and breaking up physical activities into smaller, more manageable steps ('pacing');
  • Avoiding exposure to cold temperatures;
  • Watching your diet;
  • Mobility aids (braces, scooters, walking sticks), and;
  • Pain-relief medication.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

Prevention

A polio vaccine is available and is routinely given as part of the regular childhood vaccination schedule. Adults can also receive the vaccine, if they have not previously received it. 

Polio vaccination.A polio vaccination is available for children and adults. 

Vaccine-derived polio

In very rare cases, the weakened polio virus within the vaccine has been known to cause illness, including paralysis, in the person it is given to. The virus may also infect unvaccinated people who come into contact with that person. However, it is important to remember that the benefits of the vaccine out-weigh the very rare potential risk of the vaccine. 

Some polio vaccines are administered orally.The polio vaccine can be administered orally. 

Vaccine

A preparation containing a microorganism (that causes a specific disease) in a dead or weakened state, or parts of it, for the purpose of inducing immunity in a person to that microorganism.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.

3. Jong J.C. Netter F.H and Stevens D.L. (eds) (2012) Netter’s Infectious Diseases. Philadelphia PA: Elservier/Saunders.