Elizabethkingia is often found in water and soil, but -- until now -- has seldom caused infections. So far, 54 Wisconsin residents have contracted the infection, CNN reports.
"We don't see 48 of the identical organism causing an outbreak like this very often," Michael Bell, deputy director for the Division of Healthcare Quality Promotion at the Centers for Disease Control and Prevention in Atlanta, told Wisconsin Public Radio. "In fact, this is probably the largest one we've seen."
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Rare blood infection hits Wisconsin, Michigan
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Tuberculosis: caused between 1.3 and 1.5 million deaths in 2013
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Malaria: up to 855,000 deaths in 2013
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Creuztfeldt-Jakob Disease: 100% fatal
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Middle East respiratory syndrome: 41% fatal
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Rabies: up to 100% fatal if left untreated
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Wisconsin and Michigan residents are urged to keep an eye out for symptoms such as fever, shortness of breath, chills or cellulitis. Many people who contracted the infection were over age 65 and had health problems and compromised immune systems.