What causes polio, and why is the disease reappearing in places like Yemen?
Polio (poliomyelitis, Heine-Medin disease or infantile paralysis) is an infectious viral disease that mainly affects children under age five years. The virus (poliovirus) is contracted orally and infects the intestinal lining, after which it can invade the nervous system and cause paralysis within hours. The recent polio epidemic in Yemen, as reported by the World Health Organization, represents the first cases of polio in that region since 1999. Three types of polio exist, but Type I polio is the most prevalent in Yemen. Until recently, polio vaccines immunized against Type 2 and Type 3 polio. According to the New York Times, a monovalent vaccine against Type I polio has been used in India and will soon be available in Indonesia and Egypt.Polio Causes and Symptoms
Polio mainly affects children under age five, although it can also affect adults. Early symptoms include fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in every 200 infections leads to irreversible paralysis; 5-10% of those paralyzed die when their respiratory muscles become immobilized. Polio is classed as "a disease of civilization" because it spreads through human contact, usually from fecally contaminated food or water.
History of Polio
The polio endemic has existed for thousands of years:
- The earliest known records of polio exist in Egyptian paintings of otherwise healthy people with withered limbs.
- The Roman emperor Claudius was infected as a child and thereafter walked with a limp.
- In 1840, Dr. Jacob von Heine conducted the first systematic investigation of polio, developing the theory that the disease might be contagious.
- In 1908, physicians Karl Landsteiner and Erwin Popper made the first hypothesis that polio may be caused by a virus.
- In 1921, United States president Franklin D. Roosevelt contracted polio and was paralyzed from the waist down.
- Until the 1950s, polio epidemics crippled thousands of children in industrialized countries every summer.
Polio in the United States
The incidence of poliomyelitis declined radically in the United States when a mass immunization program with the Salk vaccine - developed by Dr. Jonas Salk - was begun in 1955. By 1961 the Sabin vaccine, a preparation made from living organisms and taken orally, was released for use. Since then the disease has been virtually eliminated in the Americas, Europe, and Australasia, but vaccination programs continue because of polio's existence in other parts of the world (mainly South Asia and parts of Africa) and the ease of travel.
Click here to read quotes by Jonas Salk.
Polio Vaccination
There is no cure for polio. However, it may be prevented through multiple doses of vaccine. Given to a child, the polio vaccine will protect for life. The first mass inoculations against polio were given to children in Pittsburgh, Pennsylvania in 1954. During the late 1950s and early 1960s, these inoculations virtually eliminated polio from the industrialized world. Starting in the 1970s, routine immunizations were introduced in most countries, so that today polio occurs only in a few areas around the world.
In 1988 the World Health Organization began a global vaccination campaign to eradicate the disease, which continued to paralyze hundreds of thousands of children each year, by 2000. Although the date of eradication was later pushed back to 2005, by 2003 there were less than one thousand new cases of polio worldwide. In 2003-4 the campaign was temporarily slowed when Muslim states in Nigeria refused to use vaccines they believed would sterilize women, leading to an increase in cases there and in neighboring countries.
A Recent Outbreak
A recent outbreak of polio in Yemen was the first instance of the disease in that country for at least nine years. The number of Yemen infections stood at 22 on 29th April 2005 and had reached at least 63 by 11 May 2005.
The following table lists the current number of polio cases in the world today
(as of 11 May 2005), according to PolioEradication.org:
| Country |
Number
of cases |
| |
77 |
| |
24 |
| |
22 |
| |
14 |
| |
7 |
| |
5 |
| |
4 |
| |
1 |
| |
1 |
| Global
Total |
155 |
Useful Links
World Health Organization (WHO) - Poliomyelitis
Global Polio Eradication Initiative newsletter (English and French)