Though Emily (not her real name) was nearly 10 when she contracted polio, she has almost no memory of her illness, nor does she want to recall it. Her mother told her, "Forget, forget!"--and Emily forgot.
Glimmerings of an endless summer in the hospital and a machine that helped her to breathe sometimes surface in her dreams. Long after she was well, when she was grown up, her mother mentioned that at one point the doctors didn't know whether she would liver or die.
Emily made a complete recovery from this sometimes paralyzing disease and was able to block out the memory of those days. But now, 40 years later, unwelcome reminders of her childhood illness are returning. She finds it increasingly difficult to walk, especially when she is overtired--which is often--and to breathe while sleeping.
More than half of the estimated 250,000 to 650,000 Americans who had paralytic poliomyelitis 30, 40, even 70 years ago are now reexperiencing some of their old symptoms in what is known as post-polio syndrome. They complain of increasing muscle weakness, joint and muscle pain, fatigue, breathing difficulties, loss of stamina, low back pain, and intolerance to cold. In at least 1 out of 25 survivors, the symptoms are disabling.
While some of these complaints may be due to aging and years of abnormal stress on weight-bearing joints in those who needed mechanical assistance to walk, this does not explain the progressive muscle weakness and muscle atrophy (wasting). Although researchers are still not sure what causes post-polio syndrome, most agree with Lauro Halstead, M.D., director of the National Rehabilitation Hospital's Post-polio Program in Washington, D.C.--and a polio survivor himself--who says: "The most widely held theory is that the new muscle weakness is related to overuse of polio-damaged nerve cells in the spinal cord."
Polio's Three Strains
Thanks to an effective vaccination program, polio has been nearly eradicated in the United States. However, as recently as the 1950s, epidemics terrorized the nation, especially in the summer months, leading to the closing of public pools and other places where people congregated (see accompanying article).
Polio is a highly contagious disease caused by a virus that has three distinct strains, called types I, II and III. Immunity to one type doesn't confer immunity to the other two. Type I, the strain that causes the most paralysis, is also the cause of most epidemics.
Polio epidemics in temperate climates occurred most frequently in the summer and early fall--the poliovirus flourishes in warm weather. Children were more often affected than adults, which is why the disease was once known as infantile paralysis. Persons at greater risk for serious neurological damage during epidemics due to lowered immunity included those who had recent inoculations or recent operations, especially removal of tonsils and adenoids (because the virus invades the body through the mouth and multiplies in the throat). Pregnancy also predisposed to paralytic polio infection.
The virus is found throughout the world, but primarily in undeveloped countries with insufficient immunization practices. It is excreted in large amounts in the feces of someone who has polio or is recovering from it, and is probably spread through hand-to-hand or hand-to-mouth contact. After entering the mouth, the poliovirus multiplies in the throat and intestinal tract. Viruses may cross from the intestinal tract into the bloodstream. They are carried to the spinal cord, where they may kill or transiently injure motor nerve cells that control skeletal muscles, causing paralysis.
Sometimes only a small group of muscles is affected, sometimes the paralysis is widespread. The legs are affected more often than the arms, but polio may partially or completely paralyze a single limb, one half of the body, even all four extremities. …