Benign-turned-deadly bacterium baffles scientists

BOSTON — A deadly infection that has now spread to three states is puzzling disease investigators. The illness is caused by Elizabethkingia anophelis, a bacterium commonly found in soil and water and that, until now, has rarely caused problems.

Public health authorities in Wisconsin first reported the outbreak to the U.S. Centers for Disease Control and Prevention in early January. At that time, six people were ill with symptoms that include fever, difficulty breathing and cellulitis. The outbreak has now spread to 63 people in Wisconsin, one in Illinois and one in Michigan. Most patients are over 65. About 30 percent have died from the infection.

An investigation team led by the CDC has been unable to determine how the E. anophelis is spreading or why it has become so fatal. It was first found in the gut of a mosquito in 2011, but it does not appear to be spread by mosquitoes. (As one investigator said, the outbreak started in winter in Wisconsin, when mosquitoes are few.)

Other common connections have also been ruled out, including person-to-person spread, contaminated food or water or a tainted health care or personal product. A few other reported cases have occurred in health care settings in Asia and Africa, but the U.S. outbreak is occurring largely among people not hospitalized.

“I don’t have any answer for you about the source of this outbreak,” said the CDC’s Maroya Walters, who discussed the infection June 19 at ASM Microbe 2016, a meeting of the American Society for Microbiology and the Interscience Conference on Antimicrobial Agents and Chemotherapy.