Casadaban was conducting laboratory research on the bacterium that causes the plague when he became sick. The germ was genetically weakened and considered harmless to humans. It was considered so safe, Casadaban’s work with the live plague bacteria wasn’t noted when he fell ill, according to the CDC. A professor at the university for 30 years, by all accounts he had followed the proper safety protocols, the report said.
[...] An autopsy found the researcher had a medical condition called hemochromatosis, which causes an excessive buildup of iron in the body, according to the CDC report. The disorder affects about 1 in 400 people and goes unnoticed in about half of patients.
Casadaban’s illness is important because of the way the plague bacterium had been weakened. Yersinia pestis needs iron to survive. Normally it gets this iron by stealing it from a host’s body with proteins that bind to it and help break it down. To make the bacterium harmless, scientists genetically stripped it of the proteins needed to consume iron.
It seems hemochromatosis may not be the protection against Yersinia pestis its been made out to be.