Polio

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 20^th 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 organizations 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.

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 (feces). In a minority of cases, the virus enters the body's nervous system, causing nervous system symptoms.

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.

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 feces 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.

Types of treatment

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

• Pain-relief medications, such as acetaminophen 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.

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.

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.

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.

References

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4. Callaway E. (2011). Public health: Polio clings on in Pakistan. Nature News 473: 427428.
5. CDC Features - A Polio-Free U.S. Thanks to Vaccine Efforts. Accessed 22 July 2014 from link here
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10. John T.J. & Vashishtha V.M. (2013). Eradicating poliomyelitis: Indias journey from hyperendemic to polio-free status. The Indian Journal of Medical Research 137: 881894.
11. Larson H.J. & Ghinai I. (2011). Lessons from polio eradication. Nature 473: 446447.
12. Polio and infectious diseases of the anterior horn. Accessed 23 July 2014 from link here
13. Polio and Post-Polio Syndrome. Text. Accessed 22 July 2014 from link here
14. Poliomyelitis - Blue Book - Department of Health Victoria Australia. instructional. Accessed 23 July 2014 from link here
15. Poliomyelitis (Polio) - Online Medical Encyclopedia - University of Rochester Medical Center. Accessed 23 July 2014 from link here
16. Post-Polio Syndrome Information Page: National Institute of Neurological Disorders and Stroke (NINDS). Accessed 22 July 2014 from link here
17. WHO | Poliomyelitis (polio). WHO. Accessed 22 July 2014 from link here
18. WHO | What is vaccine-derived polio? WHO. Accessed 23 July 2014 from link here
19. Within reach. (2014). Nature 511: 263264.

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