Medical officials say an organ donor infected four transplant patients at three Chicago hospitals with the AIDS virus.
The chief of the transplantation program at the University of Chicago Hospitals says his staff was told of the problem on November 1st, and brought in the two patients who had transplants there for testing the next morning.
Tests on the donor for HIV, hepatitis and other conditions had come back negative, most likely because the donor had acquired the infections in the last three weeks before death.
The transplants occurred in January.
A spokesman for the United Network for Organ Sharing says there has not been another known case of HIV being transmitted from a donor to a recipient since federal high-risk donor guidelines were adopted in 1994.