Some survivors of a once-feared disease now face difficult new challenges.

Some 45 years ago it appeared that the world, or at least America, had been saved from the scourge of poliomyelitis. It was the dreaded “infantile paralysis” which had killed and crippled so many, including the late president Franklin Roosevelt.

The Salk and Sabin vaccines had been developed and pressed into service, sometimes with doubts in many corners. In Lawrence, for example, there were many who hesitated to get the vaccines for fear of side-effects. Then, as word of the lack of “kickback” spread, lines at clinics began to grow. Turnouts here became heavy.

Now the issue is back with us in the form of post-polio syndrome. A surprising number of people who may have contracted and recovered from polio years ago are having problems. By some public health estimates, as many as 40 percent of the nation’s 600,000 polio survivors have been beset by the syndrome, a condition marked by extreme muscle weakness and fatigue.

When the first vaccines went into use in 1955, results were dramatic. Polio epidemics had paralyzed or killed thousands, both children and adults, during outbreaks, particularly in the 1930s, 1940s and early 1950s. Iron lungs were used to keep the stricken alive. There were various treatments designed for recovery. It was a frightening time.

As William Hathaway says in the Hartford, Conn., Courant: “The polio virus infected people who had ingested minute amounts of fecal matter from contaminated water or unsanitary facilities. Panicked parents kept children away from swimming pools and other public places during outbreaks.”

There were numerous tragedies, but there also were recoveries. We’re told that these resulted when various nerve cells of victims compensated for the loss of others by making more connections than normal to muscle groups. But that has taken a toll on some, leading to the current post-polio difficulties.

Dr. Phil Arnold, a physician specializing in physical medicine and rehabilitation, says that in many cases, polio survivors wound up with no reserve of nerve cells. As they lost existing cells to aging, they became more susceptible to muscle fatigue and weakness.

Many recovered victims have had no problems to date. While there is no major treatment or cure, there is a knowledge of what not to do.

Before medical people began to understand post-polio syndrome, apparent victims were told to exercise strenuously to restore muscular strength. Excessive exercise, however, only made the symptoms worse.

Just as medical people were baffled for so many years by the polio epidemics of the past century, so are the warriors in this new polio battle — the doctors and the victims.

It seems so terribly unfair that those who have managed to defeat polio in the past are now forced to combat the problem again. And doctors remain just as frustrated now as they were in the past.