Polio is a communicable viral disease and can cause paralysis, difficulty breathing and even death. There are two types of polio: non-paralytic and paralytic. Within the paralytic type are three specific viruses named for the area of body it attacks: spinal polio which attacks the spinal cord; bulbar polio which attacks the brainstem; and bulbospinal polio which attacks both the spine and the brainstem.
Causes and Symptoms of Polio
Infected people will not necessarily show symptoms of polio. About 90% of infections cause no symptoms at all. People who contract the nonparalytic polio virus usually develop mild flu-like signs. The following signs can last one to ten days:The polio virus only inhabits humans and enters the environment through an infected person’s feces. The virus spreads through fecal-oral means. It can be transmitted through contaminated water and food or direct contact with an infected person. Carriers of the virus can spread it for weeks in their feces.
- Sore throat
- Back pain or stiffness
- Neck pain or stiffness
- Pain or stiffness in the arms or legs
- Muscle spasms or tenderness
Those who develop paralytic polio, the more rare form of the virus, usually develop signs and symptoms of nonparalytic, but within a week, the specific symptoms of paralytic start to appear. Those symptoms include:
- Loss of reflexes
- Severe muscle aches or spasms
- Loose and floppy limbs (flaccid paralysis), often worse on one side of the body
The onset of paralysis may be sudden with the paralytic virus.
Some people continue to have symptoms after recovering from the disease. It can last an average of 25-35 years. Common post-polio symptoms include: progressive muscle or joint weakness and pain; general fatigue and exhaustion after minimal activity; muscle atrophy; decreased tolerance of cold temperatures; sleep-related breathing disorders such as sleep apnea; and problems with breathing and swallowing.
Polio Vaccine Virtually Eradicates the Communicable Disease
There is no cure for the polio virus, but the disease has been held at bay in most countries with prevention measures. 1979 marked the last naturally occurring polio in the United States. Globally, the virus still continues to affect children in Afghanistan, Pakistan, Nigeria and India. While it had been stopped in Chad and Democratic Republic of the Congo, according to the Center for Disease Control (CDC), it has been reintroduced and is spreading in those two countries.
The eradication of the disease is due to the polio vaccine campaign across the world. The disease was one of the most feared in the twentieth century. In the Credit: photo courtesy of the University of PittsburgU.S. alone, 35,000 people each year were crippled with the disease in the late 1940s and into the early 1950s. Two vaccines are used: the inactivated virus injection (IVP) and the active oral version (OPV).
In 1952 Jonas Salk from the University of Pittsburg developed the first effective polio vaccine. After several years of field study, the results were announced in April of 1955. Researchers had already identified three different serotypes of the virus, labeled PV1, PV2, and PV3. The Salk vaccine test results showed it was 60-70% effective against PV1 and over 90% effective against PV2 and PV3. In addition, the vaccine was 94% effective against developing bulbar polio.
The vaccine was soon licensed for use and a children’s vaccination campaign was launched. In the U.S. the March of Dimes heavily promoted the immunization campaign and the annual number of cases of the disease dropped from 35,000 in 1953 to 5,600 just four short yeaCredit: photo courtesy of the March of Dimes Foundationrs later. By 1961 only 161 cases were reported in the United States.
In November, 1987 an enhanced-potency IPV was licensed in the U.S. and is currently the vaccine preferred. The first dose is given between one and two months old; a second dose at four months; a third dose between six and eighteen months old. A booster shot is given at age four to six. In some countries a fifth dose is given during adolescence. Adults in developed countries are usually already immune to the disease and thus no vaccine is required. In 2002 a combination vaccine was approved for use in the U.S. It contains a polio vaccine in addition to vaccines for diphtheria, tetanus and acellular pertussis and hepatitis B.
Oral vaccines were developed by several groups including Albert Sabin. His vaccine was chosen to be distributed worldwide. Licensed in 1962, the trivalent OPV beCredit: photo courtesy of the CDCcame the preferred vaccine in the U.S. and the majority of other countries across the globe. In the years 1962-1965 approximately 56% of the population in the U.S. received the Sabin vaccine. More than 95% of recipients of three doses of the OPV produce protective antibody to all three poliovirus types.
A major concern with the OPV is its ability to revert to a form that can achieve neurological infection and cause paralysis. Symptoms are indistinguishable from symptoms caused by the wild polio virus. Though it is a rare occurrence, many countries have discontinued the use of OPV once the threat of epidemic infection is curtailed, and gone back to the IVP. In 2000 the U.S. discontinued use of OPV and Credit: photo courtesy of the CDCin 2004 the United Kingdom followed. However, OPV does continue to be used around the world.
While polio has been eradicated in most countries, there continues to be problems in some. The resurgence of the disease in countries such as Nigeria is a concern. Epidemiologists believe the resurgence in these areas of Africa is due to refusals by specific local populations to allow their children to be vaccinated.
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- en.wikipedia.org (accessed February 10, 2013)
- cdc.gov (accessed February 10, 2013)
- medicalnewstoday.com (accessed February 10, 2013)
- kidshealth.org (accessed February 10, 2013)
- fundinguniverse.com (accessed February 10, 2013)
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