Public health officials are investigating the deathbr of a University of Chicago researcher who studied plague bacteria andbr was found to have the microbe in his blood, university officials said onbr Monday.br br Malcolm Casadaban, who died on September 13, was researching a weakenedbr strain of the plague bacteria Yersinia pestis. Because it is missing keybr proteins, the strain is not normally harmful to people.br br Medical center spokesman John Easton said Casadaban had the laboratorybr strain of Yersinia pestis in his blood, suggesting he had a form of thebr infection known as septicemic plague, which can kill even before thebr symptoms begin.br br Yahoo! Canada News ca.news.yahoo.