The trouble is that this virus may proceed to the blood stream and into the central nervous system causing muscle weakness and often paralysis. Eradication efforts led by the World Health Organization have reduced the number of annual diagnosed cases from the hundreds of thousands to around a thousand. Another problem with this disease is Post-Polio Syndrome - a condition that can strike polio survivors anywhere from 10 to 40 years after recovery from an initial attack of polio. In the US, the last case of "wild" polio (naturally circulating polio that is not caused by the oral polio vaccine) was in 1979 and, except some occasional importations, all cases of paralytic polio since then have been caused by the oral polio vaccine.
Spreading and paths of infection
Polio represents a highly communicable disease which is even categorized as a disease of civilization. It is proven that Polio spreads through human-to-human contact, usually entering the body through the mouth. In most cases this happen due to fecally contaminated water or food. Poliovirus is a small RNA virus that has three different strains and is extremely infectious. The virus invades the nervous system, and the onset of paralysis can occur in a matter of hours. While polio can strike a person at any age, over 50 percent of the cases occur in children between the ages of 3 and 5.
Symptoms of polio infection
The incubation period of polio, from the time of the first exposure to the first symptoms, ranges from three to thirty five days, meaning that Polio can spread widely before an outbreak is apparent.
After the initial infection with poliovirus, virus particles are excreted in the feces for several weeks and are highly transmissible to others in a community.
Polio is a viral illness that, in about 95% of cases, actually produces no symptoms at all. This type of infection is called asymptomatic polio. Symptomatic polio acounts for about the 4% to 8% of all cases. The early symptoms of infection are fatigue, fever, vomiting, headache and pain in the neck and extremities.
The illness appears in three forms:
- A mild form called Abortive polio. Most people with this form of polio may not even suspect they have it because their condition is limited to mild flu-like symptoms such as mild upper respiratory infection, diarrhea, fever, sore throat, etc.
- A more serious form associated with aseptic meningitis called Nonparalytic polio. It is found that 1% to 5% of these patients show neurological symptoms such as sensitivity to light and neck stiffness
- A severe-most serious and debilitating form is called Paralytic polio and it occurs in 0.1% to 2% of cases. In paralytic polio, the virus leaves the intestinal tract and enters the bloodstream, attacking the nerves. The virus may affect the nerves that control the muscles in the limbs and the muscles necessary for breathing, causing respiratory difficulty and paralysis of the arms and legs.
People who have Abortive polio or Nonparalytic polio usually make a full recovery. However, paralytic polio can even result in death.
The virus can affect the motor neurons that control the various muscles of eyeball movements; the trigeminal nerve and facial nerve which innervate cheeks, tears, gums, and muscles of the face; the glossopharyngeal nerve which in part controls swallowing and functions in the throat, tongue movement and taste; the nerve that sends signals to the heart, intestines, and lungs; and the accessory nerve that controls upper neck movement. If the virus affects some of these muscles it is called bulbar polio. It is a very serious form of polio with the mortality rate that ranges from 25 to 75 percent.
Post-Polio Syndrome is a strange syndrome that can strike polio patients anywhere from 10 to 40 years after recovery from an initial attack of polio. PPS is usually a very slow progressing condition characterized by a weakening of the muscles that were previously injured by polio.
Although there are many theories that tried to explain PPS, the fact is that doctors don’t know what causes it. Here are the three theories about PPS that are most likely according to research done so far:
- The first theory says that the polio virus reactivates it self again after decades of lying dormant in the patient’s cells. It is still uncertain what activates it.
- The second possibility is the evidence of disbalances in the production of various hormones and neurotransmitters in brain.
- The third theory is saying that the nerve cells that were undamaged or partly damaged took over the functions of the dead cells. Over time, these cells become overworked and lead to polio-like symptoms.
Incidence of the condition
Of the 300,000 polio survivors in the US, 1/2 to 1/4 will have symptoms of PPS. If the initial bout with polio was severe, there is a greater chance of developing post polio syndrome.
The symptoms of PPS mimic those of the original disease. The symptoms may include:
- Muscle weakness
- Muscle atrophy (stiffening)
- Painful joints and muscles
- Low back pain
- Sensitivity to cold and heat
- Sleep disorders
- Difficult breathing and/or swallowing
- Muscle twitching
It is proven that patients who had mild symptoms of polio will have mild symptoms of PPS.
Unfortunately, there is currently no effective treatment for the syndrome itself, but, a number of studies have shown that specific exercises can improve muscle strength.
Some studies have also shown that intravenous immunoglobin may reduce the pain, increase the quality of life, and improve strength. Most experts from this field think that the future of PPS treatment should center on nerve growth factors which makes sense since PPS may result from the degeneration of nerve sprouts and helping their regeneration may be the solution.
There are several strategies that are proven to be beneficial to patients:
- If you are experiencing increasing muscle weakness, exercise may be needed. Please consult your doctor.
- Eat a well-balanced diet
- Be alert to the changes in the body
- Take note of any new symptoms or any clear or gradual changes
- Take time to sleep enough
- Pace yourself
- Use medical equipment such as canes or crutches or other adaptive medical equipment to ensure that you do not fall
- Avoid weight gain
- Minimize alcohol use
- Take common colds very seriously
- Get regular checkups with emphasis on the major areas affected by the polio: neuromuscular, circulatory and respiratory, as well as, muscle strength evaluations
- Discontinue any exercise that causes pain, weakness or muscle fatigue
- Know your own strengths and limits
- Get involved or continue with physical therapy
In the United States, it's currently recommended that children have 4 doses of inactivated polio vaccination between the ages of 2 months and 6 years.
This vaccine is developed by Albert Sabin in 1964. The Sabin vaccine is a live-attenuated vaccine, produced by the passage of the virus through non-human cells. Although it is very effective the problem with OPV was that, in very rare cases, paralytic polio could develop either in immunized children or in those who came in contact with them. IPV is given by injection. It protects vaccinated persons as well as OPV, but it is not believed to be as effective as OPV in preventing the spread of polio virus among non-vaccinated persons.
IPV is a vaccine that stimulates the immune system of the body to fight the virus if it comes in contact with it.
Polio complications include paralysis, most commonly of the legs but paralysis of the muscles that control breathing and swallowing are a bigger danger and can even be fatal.
In very rare cases, the oral vaccine used to prevent polio can cause polio paralysis in persons who are vaccinated and in people who are in close contact with them. About 8 to 9 cases of paralytic polio caused by the oral vaccine have been reported in the United States yearly.