Five years before 39-year-old Franklin Delano Roosevelt was diagnosed with polio, the paralyzing disease struck thousands in the U.S., killing some 6,000. During the 1916 epidemic, 9,000 cases occurred in New York City, which called for quarantines. Polio would haunt the country for decades, afflicting thousands each year; TIME wrote in 1946 that "for many a parent who had lived through the nightmare fear of polio, there was some statistical encouragement: in 1916, 25% of polio's victims died. This year, thanks to early recognition of the disease and improved treatment (iron lungs, physical therapy, etc.) the death rate is down to 5%." It was only in the 1950s that Dr. Jonas Salk finally developed a vaccine.