Lewis was one of three 1964 San Francisco 49ers teammates who died of amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, a rare ailment with an incidence estimated at 1 per 50,000 individuals in the general population.[1] Others 49ers stricken by the disease included contemporaries Bob Waters and Matt Hazeltine and — a generation later — wide receiver Dwight Clark.[1]
Studies have been done examining the use of DMSO, painkillers, and the fertilizer used on the 49ers practice field in Redwood City, California in an effort to isolate a potential chemical connection.[1] A possible connection between the disease and mild traumatic brain injury (concussion) is a matter of ongoing study.[2]
