Sudan Sunrise director Tom Prichard says the 7-foot-6 Bol is in "critical care." He says Bol "had a total kidney failure" and has developed Stevens-Johnson Syndrome, which has caused Bol to lose patches of skin.
Bol was returning to the United States last week from his native Sudan after helping fight corrupt practices in the country's recent elections. He was hospitalized during a stopover in Washington.
Prichard says he thinks Bol is "going to pull through" but may have to be moved to a burn unit.
The 47-year-old Bol played 10 seasons in the NBA.
His illness was first reported on The Washington Post website.
"He's pleased that he accomplished what he was so determined to do in Sudan," Prichard told the Post. "He was fighting with every bit of his strength to try to keep southern Sudan on course towards a referendum in January of next year. . . . It put him right on the edge of survival, and he made it."