On Sept. 13, University of Chicago geneticist Malcolm Casadaban died from an infection which has been attributed to a weakened laboratory strain of Yersinia pestis, the bacteria that causes the plague. Sixty- year-old Casadaban was working with Y. pestis, and other unspecified bacteria, for a genetic study.
According to a statement from the University of Chicago Medical Center, the laboratory strain of Y. pestis was found in blood samples taken from Casadaban after he was admitted to the Medical Center’s Bernard Mitchell Hospital. The finding suggests the possibility that Casadaban died from a form of infection known as septicemic plague, which can lead to death before any other physical symptoms of the disease develop.
Kenneth Alexander, chief of pediatric infectious disease at the medical center, described the case as a mystery. In a statement from the medical center, Alexander said that the bacterium is not typically fatal. The laboratory strain is engineered to lack the key proteins that cause it to be harmful to humans. The strain is considered so safe that it has even been used in some countries as a live-attenuated vaccine against the disease. The strain is approved by the Centers for Disease Control and Prevention (CDC) for routine laboratory use.
The infection control team at the medical center is working with the Chicago Department of Public Health (CDPH), the Illinois Department of Public Health, and the CDC to investigate Casadaban’s death. According to the Medical Center, no other illnesses related to the case have been reported.
Officials are looking into the possibility that an underlying medical condition may have contributed to Casadaban’s death. However, the medical center has reported that the initial autopsy indicated no obvious cause of death except for the presence of the bacteria in blood cultures. According to the medical center, conditions like high levels of iron in the blood can increase susceptibility to infection.
Though the strain is not known to be deadly, officials are taking all precautions. Casadaban’s lab has been sealed off in accordance with the investigation, and on Sept. 18, the medical center began notifying family, friends, colleagues, and health care personnel who had contact with Casadaban prior to his death. "While the death of this individual researcher is terrible and tragic, there is currently no indication that his case of illness spread to anyone else," the CDPH said in a statement.
Symptoms of the plague usually develop within 2-10 days of exposure. The University has reported that none of those who had contact with Casadaban have reported any illness. The typical treatment for the disease is a course of antibiotics.
Casadaban held degrees from Harvard, Stanford, and the Massachusetts Institute of Technology. He was also a member of the University of Chicago’s Institutional Biosafety Committee, which regulates research protocols for the use of biohazardous substances.
A memorial for Casadaban was held at the University on Sept. 16. A funeral service is planned for November. “This death is a tragic loss to our community,” James L. Madara, dean of the Biological Sciences Division and Pritzker School of Medicine, and CEO of the Medical Center, said in a statement. “We are all saddened to lose a valued colleague.” Those wishing to make donations have been asked to contribute to the American Diabetes Research Association.
The plague appears in three forms, septicemic, pneumonic, and bubonic. The bubonic plague infects the lymph nodes and is infamous for the outbreak in Europe in the 1300s. Pneumonic plague infects the lungs. Septicemic plague is an infection of the blood. It is the rarest of the three forms, but considered the most lethal.
Infection due to the modified strain of Y. pestis is so rare that data regarding infection rate is unavailable. In the United States about 20 cases of plague are reported each year due to unmodified strains of Y. pestis. Plague remains a significant problem in developing countries where up to 3,000 cases are reported yearly.