University hospital officials said there "does not appear to be a threat to the public" following the death of Malcolm J. Casadaban, 60, at the campus' Bernard Mitchell Hospital on Sept. 13.
None of the people the researcher had contact with has reported illness and symptoms typically develop within 2 to 10 days, officials said.
The researcher was studying a weakened laboratory strain of Yersinia pestis that lacked the plague bacteria's harmful components, officials said.
Further study is under way after initial autopsy showed no obvious cause of death other than the presence of the bacteria.
Underlying health conditions could potentially increase susceptibility to infections, officials said. Casadaban's death notice asked mourners to make donations to the American Diabetes Research Association.
Casadaban had degrees from M.I.T. and Harvard University, according to a record of his university Web page that already had been taken down. "He was a highly respected scientist with a brilliant mind" and a "humble man of high integrity, loyalty and loving kindness," according to his death notice.
A memorial service was held at the university Wednesday, according to a Web page put up by Casadaban's daughter. A funeral service is planned for November in New Orleans, according to the death notice.
University officials said the weakened strain of the bacteria is used as a vaccine to protect against the plague.
According to university officials, the Centers for Disease Control and Prevention has approved the weakened strain for laboratory studies. It does not require special safety precautions required for work with more virulent strains, according to the release.
Once the lab strain was identified Friday, officials contacted the Chicago Department of Public Health.
They are working with that office along with the Illinois Department of Public Health and Centers for Disease Control and Prevention officials to investigate the researcher's case and take precautions.
Officials have reached out to family, friends and colleagues of the researcher. So far no one has reported being sick even though symptoms typically occur within 2 to 10 days after exposure.
Medical center officials said the plague is rare in the United States and is more frequently seen in developing countries where up to 3,000 cases are reported yearly.
-- Carlos Sadovi and Tribune staff