The transplants occurred in January at three Chicago hospitals, but the four patients who were infected with HIV and the virus for hepatitis C did not learn of their status until the last two weeks, according to medical officials.

A screening questionnaire determined the organ donor had engaged in high-risk behavior, according to officials at Gift of Hope Organ & Tissue Donation, the Elmhurst-based organ procurement agency that tested and approved the organs for donation.

But tests for HIV, hepatitis and other conditions came back negative, most likely because the donor had acquired the infections in the last three weeks before death. Personal details about the donor were not released by medical ...