(CNN) Boxing legend Muhammad Ali will be laid to rest Friday, one week after he died at age 74. Ali had been publicly battling Parkinson's disease for more than three decades, so it came as a surprise to many that his official cause of death, according to family spokesman Bob Gunnell, was "septic shock due to unspecified natural causes." "Sepsis is the body's overwhelming and life-threatening response to an infection, which can lead to tissue damage, organ failure and death," according to the Centers for Disease Control and Prevention. "A direct link from Parkinson's to sepsis is a long jump. However, there are several features of Parkinson's -- especially later in the course of the illness -- that can place a patient at higher risk for [developing] an infection, which can get into the bloodstream and cause them to become septic," said Dr. Michael S. Okun, national medical director of the National Parkinson Foundation.Muhammad Ali died of septic shock, according to his family's spokesmanSepsis is not typically linked to Parkinson's disease but rather an infection
"_ is a common complication of people hospitalized for other reasons."