City health officials and the University of Chicago Medical Center on Sunday began the precautionary measures of offering antibiotics to the family, friends and co-workers of a geneticist who died last week of exposure to a plague-related bacterium.
Infectious disease experts couldn't rule out the possibility that the federally approved weakened strain of Yersinia pestis that Malcolm Casadaban was researching at the University of Chicago had somehow become dangerous.
But largely because nobody else exposed to the bacterium or to Casadaban has developed plague symptoms, it seems more likely there was something about the professor's health or genetic makeup that made him susceptible, officials said Sunday.
Further study is under way after an initial autopsy showed no obvious cause of death other than the presence of the bacterium, officials said.
"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 Chicago Department of Public Health said in a statement. "There is currently no indication of a threat to public health."
Casadaban, 60, was working with a strain of Yersinia pestis that, stripped of its harmful components, has been used as a vaccine against the plague since the late 1960s.
Once the world's worst health scourge, the plague today affects 1,000 to 3,000 people per year, with most of the 10 or 15 annual cases in the U.S. occurring in rural areas of the Southwest where rodents carrying the bacterium are more common, according to the federal Centers for Disease Control and Prevention.
Casadaban, a renowned molecular geneticist with a passion for research, had been working to develop an even stronger vaccine for the plague, said his daughter Leigh, 21.
"He was a brilliant, brilliant guy," she said of her father. "He had such a love for genetics."
On the morning of Sept. 13, Casadaban developed intense flulike symptoms and arrived at the emergency room of the university's Bernard Mitchell Hospital, hospital officials said. He died 12 hours later.
Initially, doctors did not know they had a plague case on their hands, said Dr. Ken Alexander, chief of pediatric infectious disease at the medical center.
After blood test results came back Friday, the hospital notified city and state public health officials, he said.
Alexander -- who compared the bacterium Casadaban was working with to a "crocodile that doesn't have teeth" -- said the risk for an outbreak is very low.
"The more likely possibility, I'd say 999 to 1, is that there was something unusual about him," Alexander said, explaining that other strains of Yersinia bacteria linked to intestinal disease have been known to prey on people with abnormalities in their iron metabolism.
"As colleagues, we all feel we owe it to this man to find out what was different about him," Alexander said. "Given his field of research, I think that's what he would have wanted."
Casadaban's family said they were not aware of any pre-existing health problems that would have made him more susceptible to the weakened bacterium.
They remembered Casadaban as a fitness enthusiast who rode his bike to work every day and considered a family day at the Six Flags amusement park a great opportunity to log in some walking miles.
A native of New Orleans, Casadaban enjoyed teaching his family about genetics, said Leigh Casadaban, herself a genetics student at her father's alma mater, the Massachusetts Institute of Technology.
"He made it seem like it was all fun," she said.
Casadaban's other daughter, Brooke, 28, remembers her father as the quirky relative who showed up to family gatherings in New Orleans with new microscopes or math problems for his nieces and nephews.
Among the many topics Casadaban loved to expound upon -- the obesity gene, the "basic" nature of cloning -- her father's favorite was the notion that human beings are destined to live longer, Brooke Casadaban said.
"He really believed that life would last longer in the future," she said, noting the random nature of her father's passing. "None of us were prepared for this."
Answers to your plague questions
The CDC breaks down how plague is spread, where it is found, more: chicagotribune. com/plague