Cases are popping up around the state, but the infection seems to be coming from a single source.
So far, over 50 people in Wisconsin alone have been infected with a mysterious type of bacteria called Elizabethkingia meningoseptica, and since November, 15 of them have died.
To put that into perspective, PBS reports that each state only sees about 6 cases of Elizabethkingia infection every year, so an outbreak of this multitude is unprecedented, to say the least.
"The fact that we’re seeing more than four dozen cases, that is a very large outbreak," Michael Bell, deputy director of the Centres for Disease Control and Prevention's (CDC) healthcare quality division, told WIRED. Bell says that cases of Elizabethkingia usually pop up in ones or twos.
What’s so strange is that the bacterium isn’t known to make people sick on this scale — typically, once it makes its way to a person’s bloodstream, it can cause fever, chills, shortness of breath, and cellulitis, which is a bacterial skin infection.
In the worst cases, Elizabethkingia can cause sepsis, which is a life-threatening illness caused by the body responding to an infection. Sepsis can be particularly deadly in patients who have existing diseases or weak immune systems, and most of the patients who have died from Elizabethkingia during the current outbreak have all had pre-existing conditions and were over the age of 65.
How did all of these people get infected? That’s the golden question that researchers are frantically trying to answer.
"At this time, the source of these infections is unknown and the department is working diligently to contain this outbreak," the Wisconsin Department of Health Services announced to the press.
In previous cases of Elizabethkingia infections, experts have been able to narrow down the outbreak to a single source — for instance, a report published by researchers in London linked cases of the disease in a UK critical care unit to contaminated tap water.
The current outbreak in Wisconsin, however, involves patients spread across 12 different counties, and they were all infected in a range of different situations — some were infected in their own homes, some in nursing homes, others in hospitals.
Adding to the mystery, a genetic analysis of the bacteria suggests that all of these infections are coming from a single source.
An obvious guess based on previous Elizabethkingia cases would be that the Wisconsin tap water had been contaminated, but researchers tested the water supply and found no signs of contamination.
"That leaves us looking at a huge number of potential risk factors," including medications, foods and environmental sources, Bell told The Washington Post. "It’s frustrating. The fact that all these cases share a fingerprint has us wanting to really track down the source."
The CDC has put 70 to 80 researchers up to the challenge of identifying the source of the outbreak, with eight experts working directly in Wisconsin.
They plan to continue analyzing the local water, as well as produce at grocery stores that could have been contaminated with water while it was washed. Obviously, that kind of analysis is lengthy and tedious: "The amount of potential exposure sources is very large," Bell told WIRED.
To add to the urgency of the situation, Michigan State University microbiologist Dr. Shicheng Chen tells Vox that the bacteria seem to be resistant to antibiotics and disinfectants.
"Our studies show that Elizabethkingia acquired some antibiotic-resistant genes that we originally thought were not supposed to be there," Chen told Vox. "That means Elizabethkingia are quickly adapting to antibiotics."
He says the disease is understudied, so there’s still a lot to learn about it. For now, all we can do is hope that researchers will get to the bottom of the mystery and that people in the affected areas stay safe.