Polio was once a parent's worst nightmare - it paralyzed young children without warning.
In 1950, when Rick Kneeshaw was 3 ½ he came down with a high fever. His parents brought him to the hospital, where doctors told them Kneeshaw probably had polio.
"And they said, well, how will we know?," Kneeshaw recalled, "and they said, well, take him home tonight, and then first thing in the morning, go into his room and stand him up in his crib, and if he falls over, he's got polio."
Soon after Kneeshaw was diagnosed, his mother found out about a hospital in Los Angeles for crippled children.
The hospital became Kneeshaw's second home.
"And over the next 12 years" Kneeshaw said, "by the time I was 16, I'd had 12 orthopedic operations, and I'd spent a total of four and a half years in the hospital."
In the early 50s, tens of thousands of American kids were stricken with polio. Many, like Kneeshaw, were left paralyzed. Some died when the disease spread to the muscles that control breathing.
Pediatrician H. Glenn Kellogg started working in San Diego in 1950. He said parents of young children were really frightened.
Dr. Kellogg was head of pediatrics at the old County Hospital from 1957 to 1961.
"We had people in iron lungs," Kellogg said, "and people being treated with the 'Sister Kenny' hot flannel treatment, where the room was filled with steam, and every four hours they'd put wet flannel pads on people with paralyzed extremities to relieve some of the spasm and pain that they had."
In 1955, medical researchers struck back. A polio vaccine developed by Jonas Salk was released to the public. The vaccine was based on a killed polio virus.
Soon after its introduction, a mass vaccination campaign was launched in the U.S.
In 1962, an oral vaccine that contained a weakened live polio virus was added to the arsenal. Together, over the next 30 years, the vaccines helped eradicate polio in most of the world.
Dr. J. Lindsay Whitton is a virologist and immunologist at La Jolla's Scripps Research Institute. He's also a polio survivor.
Whitton said the disease is tough to eliminate. That's because the vast majority of un-vaccinated people who are infected with polio will not develop any signs or symptoms.
"And so therefore," Whitton said, "if only roughly one in 200 to one in 500 individuals develops the characteristic paralysis that we associate with polio infection, then it becomes much more difficult to the teams who are trying to administer the vaccines, to identify outbreaks of polio."
In 2009, there were 1,600 cases reported worldwide.
Some researchers believe that's as close as we're likely to get to eliminating polio. Whitton said unless we mount a massive effort to destroy polio, it will come back.
"The virus will reappear and will cause somewhere in the region of a quarter of a million cases of paralytic disease per year," he argues. "That just seems too much of a cost to bear."
In recent years, many polio survivors have faced additional health challenges.
Rick Kneeshaw said he first noticed things were changing when he reached his 40s.
"And since 1984 the strength in my good leg is now down to about 40 percent of what it was at one time," Kneeshaw said. "And so that's causing overall weakness in my body, and my arms have gotten weaker."
These symptoms are characteristic of what's become known as post-polio syndrome. The condition affects as many as half of those who suffered paralytic polio.
The polio vaccine came too late for Rick Kneeshaw. But it has prevented millions of other people from getting the crippling disease.
