Health officials are testing water, skin care products and over-the-counter medications, and interviewing patients and families, to try to identify the source of an outbreak of a bacteria that has sickened 44 people in southern Wisconsin and may have contributed to 18 deaths.
Lab tests suggest a common source of the bacteria, called Elizabethkingia. But the investigation, which started in January, has not revealed the source, health officials said.
Most of the patients are elderly, with serious underlying health conditions. No cases have been reported among children, and there is no evidence of transmission from one person to another, said Karen McKeown, state health officer.
“We have not been able to identify the common theme between all of these that would point us to the source,” McKeown said. “We are pursuing every clue.”
Dr. Chris Braden of the Centers for Disease Control and Prevention, which is assisting in the probe, described the outbreak as a particularly challenging mystery.
“We have collected a lot of data ... and haven’t identified a source or even a strong hypothesis,” said Braden, deputy director of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases. “This is a difficult one, even in the experience of doing these types of outbreaks in the past.”
The 44 cases are in the following counties: Columbia, Dane, Dodge, Fond du Lac, Jefferson, Milwaukee, Ozaukee, Racine, Sauk, Washington and Waukesha.
UW Hospital and Madison’s Veterans Hospital haven’t had any cases, and Meriter Hospital has had two since 2014, spokespeople said. Kim Sveum, spokeswoman for St. Mary’s Hospital, wouldn’t say if St. Mary’s has had any cases.
No cases linked to the Wisconsin outbreak have been reported in other states, McKeown and Braden said.
Nationwide, about 250 to 500 cases are known to occur each year, with a few localized outbreaks in recent years, said CDC spokesman Tom Skinner. The Wisconsin outbreak is the largest, he said.
Though 18 people have died, it’s not clear if their deaths were caused by the bacterial infection or their underlying health conditions, McKeown said. The conditions include cancer, diabetes, kidney disease and alcoholic cirrhosis.
Elizabethkingia bacteria rarely cause illness in humans, the state health department said. Symptoms can include fever, shortness of breath, chills or cellulitis, a skin infection.
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The first cases were reported in late December, and the investigation started in early January. The state Department of Health Services didn’t announce the outbreak until Wednesday.
McKeown said doctors and “everybody who needed to know” were notified in early January. Health officials didn’t want to alarm the public, she said.
“It’s a difficult balancing act to decide between creating concern among the public and being very transparent,” she said. “We decided that with 44 patients, it was important for the people of Wisconsin to know what was going on even if we don’t have all of the answers yet.”
Five disease investigators from the CDC joined state health investigators last month in interviewing affected patients and families and gathering samples that might help pinpoint the source.
The investigators have been visiting homes, nursing homes and other nursing facilities, Braden said. Samples are being collected for testing from water, drains, skin care and personal care products, over-the-counter medications and medicines distributed by pharmacies, he said.
The 44 patients are on different water systems, with some using wells, so the source doesn’t appear to be a water distribution system, Braden said.
The Wisconsin State Laboratory of Hygiene, part of UW-Madison, has been testing patient samples and collecting environmental samples to ship to the CDC, said David Warshauer, the lab’s deputy director of communicable diseases.
Elizabethkingia is resistant to some antibiotics, but other antibiotics are effective, McKeown said. Some patients are being treated with a combination of antibiotics, she said.
Previous outbreaks of Elizabethkingia in the U.S. have been associated with hospitals, but the Wisconsin outbreak appears to be different, Braden said.
“It looks like, for the most part, it’s being transmitted in the community somewhere,” he said.
Elizabethkingia has long been known to be in the environment, Braden said. “It can be in soil, it can be in water, it can be on surfaces,” he said.
It is named after Elizabeth King, who first reported on the bacteria in 1959 while at the CDC.
The Wisconsin outbreak involves anophelis, a species of Elizabethkingia first identified in 2011 in mosquitoes. It’s unclear if mosquitoes transmit the bacteria.