A mysterious blood infection that has killed 17 people in Wisconsin over the past four months has now been linked to the death of a Michigan resident, raising the stakes for medical investigators who are scrambling to trace the source of the outbreak.
Since November, at least 54 people in Wisconsin have fallen seriously ill with infections caused by Elizabethkingia, a bacteria that is commonly found in water and soil but very rarely causes illness in humans. When human infections do happen, they tend to occur in hospital settings and/or immunocompromised individuals, and usually involve very few cases.
But the outbreak in Wisconsin is different: while many of the patients are elderly, and all have a history of serious illness, most have not had any recent contact with hospitals, indicating that they are becoming infected in the community, which is unheard of for this type of bacteria. The infection is also affecting patients across a huge geographical area, with cases confirmed in at least 12 Wisconsin counties plus one county in Michigan.
“These patients are in different places around southeastern Wisconsin,” Dr. Christopher Braden, deputy director of the CDC’s National Center for Emerging and Zoonotic Infectious Diseases, told the Minneapolis Star Tribune. “There’s no commonality for some particular environmental exposure that people had.”
Also unprecedented is the size of the outbreak — according to the Milwaukee Journal-Sentinel, prior outbreaks of this particular strain of bacteria (Elizabethkingia anophelis) have not exceeded 10 patients.
“We don’t see 48 of the identical organism causing an outbreak like this very often,” Dr. Michael Bell, deputy director of the Centers for Disease Control and Prevention’s (CDC) healthcare quality division, told NPR. While there is no national surveillance system for Elizabethkingia cases, Bell said the current outbreak is “one of the largest that I’m aware of and certainly the largest one we’ve investigated.”
This outbreak also appears to be associated with more severe infections and more fatalities than prior outbreaks. So far, about a third of all confirmed Elizabethkingia cases in Wisconsin have resulted in death.
Depending on how the microbe infects people, sickness can look quite varied. Elizabethkingia anophelis can cause infections of the blood, leading to sepsis and septic shock. It can also attack the respiratory tract, causing lung infections and difficulty breathing, or even infect the skin, causing rashes and swelling. Both Elizabethkingia anophelis and another strain called Elizabethkingia meningoseptica are associated with infant meningitis, which researchers think can be passed on from mothers to babies. In 2011, Elizabethkingia bacteria was discovered in the guts of mosquitoes, but there’s been no solid evidence of transmission to humans in this way.
The search for the source
In the past, outbreaks have been linked to isolated sources, such as contaminated taps in hospital sinks at a London critical care unit. But what’s so confounding about this outbreak is that patients are spread across 12 different counties, with a range of living conditions – some were living in nursing homes, others in houses or apartments, and only some had been in the hospital prior to getting sick.
What’s even more mysterious is that genetic analyses of the bacteria involved suggest that all of the infections are coming from a single source, and somehow infecting people all over the southeastern and southern parts of the state.
The most obvious answer would seem to be that the Wisconsin tap water had been contaminated, but tests of the water supply have so far shown 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 now has 70 to 80 researchers working with the Wisconsin Department of Health Services to identify the source of the outbreak, with eight experts currently on the ground in Wisconsin. The disease detectives have a daunting task ahead of them that includes extensive investigations of environmental risk factors as well as interviews with surviving patients and relatives of deceased patients to look for clues as to what they all might have in common, whether it’s using the same lotions or wipes, or eating the same foods sourced from the same place.
To date, scientists have tested for the mysterious bacteria in water sources, health-care facilities, and environmental sources, but “none of these have found to be a source of the bacteria,” the Wisconsin Department of Health Services noted in a statement.
With the outbreak now crossing state lines, the pressure is on to locate its point of origin—and fast. Of particular concern to public health officials is that Elizabethkingia bacteria can withstand disinfectants like bleach, and they also appear to be resistant to many of the first-line antibiotics we have available. Because of the bacteria’s resistance to antibiotics, health officials warn that infections must be caught early on to prevent serious complications, especially among patients with underlying health conditions.
“Timely diagnosis is key to ensuring patients receive appropriate treatment, and we will continue to provide updates and guidance as additional information becomes available,” said Dr. Eden Wells, chief medical executive of the Michigan Department of Health and Human Services.