The U.S. Centers for Disease Control and Prevention (CDC) sent investigators to southern Wisconsin where a bacterial bloodstream infection has been linked to 18 deaths and 44 confirmed cases.

The federal experts will be working alongside state and local epidemiologists as well as lab workers to determine how people are contracting the infection that is caused by the bacteria, Elizabethkingia. By identifying the source of the transmission, doctors can diagnose cases more effectively, which is vital since Elizabethkingia, which rarely leads to illnesses in humans, is resistant to a lot of the antibiotics that doctors typically use.

"At this time, the source of these infections is unknown and the department is working diligently to contain this outbreak," Wisconsin Department of Health Services officials said in a press release.

The department had been notified of six potential cases of an Elizabethkingia infection during the time frame of Dec. 29, 2015, to Jan. 4, which prompted a statewide surveillance to be set up Jan. 5. The department alerted health and infectious diseases experts and laboratories across the state about the presence of the bacteria. So far the cases have been reported in these counties: Columbia, Dane, Dodge, Fond du Lac, Jefferson, Milwaukee, Ozaukee, Racine, Sauk, Washington and Waukesha.

State Health Officer Karen McKeown said the cases so far have mainly been concentrated in adults over the age of 65 and all of the people who have been infected have underlying healthy conditions. In regards to the 18 deaths, McKeown stated that, although all 18 had tested positive for the bacteria, it is currently unclear whether or not they died because of the bacteria.

Elizabethkingia would generally affect people who have compromised immune systems or preexisting health problems. Symptoms of an infection can include fever, chills, shortness of breath or a bacterial skin infection called cellulitis.

"Determining the source of the bacteria affecting patients in Wisconsin is a complex process," McKeown said. "While we recognize there will be many questions we cannot yet answer, we feel it is important to share the limited information we have about the presence of the bacteria, as we continue our work to determine the source."

Officials are expecting the number of confirmed cases to rise.