It's a paradox of public health that being too clean can sometimes lead to disease. For centuries, infants were routinely exposed to the poliovirus in their unsanitary living conditions. Polio rarely causes paralysis in infants, partly because of the maternal antibodies still present in their systems. In the 1900s, many countries cleaned up their water and sanitation systems, and houses in more affluent communities were routinely cleaned, reducing exposure to microbes. By the 1930s, '40s, and '50s, new mothers, especially those in the middle class, had no antibodies in their immune systems to pass on to their children. When children were exposed to the poliovirus in later years, they were defenseless against the disease.
Poliomyelitis, formed from the Greek words meaning "inflammation of the gray matter," is caused by an intestinal virus. Excreted in feces, the virus passes from person to person by infected water in swimming pools, lakes, and the like. It can also be transmitted if those affected with the virus fail to wash their hands after changing diapers or using the bathroom and then handle other people's food, water, or dishware. The poliovirus can survive up to two months outside the body.
Most of those infected never get seriously ill. They may feel unusually tired, stiff, and achy, but they recover quickly and assume they had a bout with the flu. When they return to school or work, the virus returns with them.
But in about 2 percent of all cases, the virus penetrates the central nervous system and attacks the neurons of the spinal cord and lower brain. Muscle weakness and varying degrees of paralysis result. If the nerves that control breathing are affected, the victim could die, or at best may require a breathing aid. As of the 1920s, that meant the infamous iron lung, the coffinlike cylinder that encased polio victims in metal, sometimes for life.
Researchers believe that polio has plagued societies for centuries. As evidence, they point to an Egyptian stele (a stone slab usually carved or inscribed for commemorative purposes). Dating from about the 15th century B.C.E., this particular stele depicts a young man with an atrophied leg, the trademark sign of polio. Medically, the disease went undescribed until the late 1700s, when British physician Michael Underwood called it a "debility of the lower extremities."
Compared to malaria, which kills more than one million people each year, and AIDS-related illnesses, which claim three million, polio has been reduced to a marginal world disease. In fact, it was never among the most fatal afflictions. Its notoriety occurred for two reasons: First, it is the only common disease that can cripple an otherwise healthy child overnight, a fact that caused hysteria among parents; and secondly, polio struck Franklin Delano Roosevelt at age 39, and he was subsequently elected president of the United States four times.
Roosevelt sought relief in the therapeutic waters of Warm Springs, Georgia. He soon bought the resort and turned it into a haven for polio sufferers. The Warm Springs Foundation, which first became the National Foundation for Infantile Paralysis and ultimately the March of Dimes, galvanized public awareness of polio and the need for financial contributions for research.
Through the first half of the 20th century, medical orthodoxy prescribed immobilizing affected limbs by splinting and casting, along with prolonged bed rest for the victim. This treatment unfortunately ensured that weakened muscles would atrophy further.
A radical new approach spread across the world, literally, in the hands of Sister Elizabeth Kenney. The former Australian army nurse developed a procedure that involved painful massages and exercises to keep muscles supple and active. Though children thought of this rigorous treatment as torture, it did seem to mitigate polio's long-term effects.
Since polio is caused by a virus, there are no medicines that can prevent or cure it. But on April 12, 1955, Dr. Jonas Salk sparked celebrations around the world by announcing the results from the largest field trial in medical history. Salk injected half of a group of 650,000 second-graders with a "killed" or dead virus vaccine and gave the other half a placebo. He also monitored another one million children as control subjects. His vaccine wasn't 100 percent effective, but it significantly cut infections, and polio was on its way to being conquered with the then-largest vaccination campaign in U.S. history. In America, incidence of the disease dropped from almost 58,000 reported cases in 1952 to just 1,000 cases 10 years later. Dr. Albert Sabin followed in 1957 with a "live" or active virus vaccine administered in sugar cubes, which children much preferred to injection and which provided longer immunity.
Mandatory child vaccinations rid the United States of the wild poliovirus by 1979. In 1988, the World Health Organization, UNICEF, Rotary International, and the U.S. Centers for Disease Control and Prevention launched the Global Polio Eradication Effort to rid the rest of the world of polio, too. Rotary members have raised millions of dollars for the effort, sending volunteers abroad to assist with vaccination campaigns.
The global immunization effort faces many obstacles. Since 1988, an army of 20 million volunteers has vaccinated two billion children in 200 countries, but getting the last scores of thousands immunized has been difficult. In Nigeria, false rumors circulated that the vaccination was purposely tainted with HIV or could cause infertility. When people stopped having their children immunized, incidence of polio rose again. In other poor countries, people wondered why so much money was being spent on eradicating polio, an infrequent disease, when local communities could better apply the resources to more pressing public health goals, such as clean water and sanitation.
Polio is proving to be a stubbornly difficult disease in another way. Decades after being quelled by vaccines, it is returning in the form of post-polio syndrome. Polio survivors from the 1940s and '50s report the reemergence of symptoms ranging from joint and muscle pain to breathing difficulties. The estimated 10 million survivors worldwide (600,000 of them in the United States) now face in their older age the threat of a second attack from the "great crippler of young adults."
The goal of preventing all new infections is in sight. In 2004, only 1,263 cases were reported, mostly in Nigeria, Niger, the Congo, Afghanistan, India, and Pakistan. That is a stunning 99 percent reduction from the 350,000 cases in 1988, when the eradication effort began. But in 2005, after pilgrims to the Hajj in Mecca may have helped spread the disease from Nigeria, new cases were reported in Yemen and Indonesia. Nevertheless, poliomyelitis may soon become the second human disease, after smallpox, to be eliminated in nature. The WHO predicts that polio will be eradicated by 2007.