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Elizabethkingia, the rare and deadly bacteria that's sickening people in the Midwest, explained

Elizabethkingia anophelis growing on a blood agar plate. (CDC)
Elizabethkingia anophelis growing on a blood agar plate. (CDC)

Since last November, more than 50 people in Wisconsin have been sickened by mysterious bacteria called Elizabethkingia anophelis. This is the largest recorded outbreak caused by what's to date been a rare microbe — and the same bug was identified last week in a patient who died in Michigan.

Public health officials in both states don't yet know what sparked the outbreaks or how people became infected, but they're worried. So far, 18 people have died from the infection, and researchers believe this particular strain is resistant to many of the antibiotics that could stop it.

There's another problem: There's a lot the research community has yet to learn about Elizabethkingia and its effects on people. I spoke to one of the few researchers — Michigan State University microbiologist Dr. Shicheng Chen — who's studied the species that's sickening people in the US. Here are five facts to know.

1) The bacteria were only discovered in 2011

In case you were wondering, Elizabethkingia (pronounced Eleeza-beeth-kin-gea) is a type of bacteria named for Elizabeth O. King, a bacteriologist at the US Centers for Disease Control and Prevention who discovered the first species of this genus in the 1950s.

Since then, researchers have found several related bacteria. The one that's currently circulating in the US is Elizabethkingia anophelis, which was isolated from from Anopheles mosquitoes in 2011.

2) The bacteria are everywhere, but they don't sicken everyone

Dr. Chen explained that these bacteria are common — found in soil, water, and insects — and only rarely seem to bother humans. Typically, the people who get sick are the very young, the elderly, or those with underlying health conditions.

And that's exactly what seems to be playing out in the US. In Wisconsin's outbreak, which has been going on since November, 54 people have been infected and 17 have died. Most of the patients who were diagnosed with the bug were over the age of 65 (the median age is 77). Additionally, all of those infected had a history of at least one underlying serious illness that compromised their immune systems.

In Michigan, the Department of Health and Human Services said the patient who was infected with Elizabethkingia — and who later died — was an older adult with underlying health problems.

3) Elizabethkingia can kill

In all the US cases, it's unclear whether the bacteria caused or contributed to the deaths. But Elizabethkingia can be deadly. Chen said the death rate from this bacteria is usually around 20 percent (though some outbreaks have killed more than half of those infected). Again, though, most outbreaks to date have been a lot smaller than the one we're seeing in the Midwest.

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 meningoseptica and anophelis are associated with infant meningitis, which researchers think can be passed on from mothers to babies.

For most healthy people, however, Elizabethkingia doesn't seem to be much of a problem. "It's just some patients — especially those who are old, normally around 65, or who are immunocompromised — who have trouble," said Chen.

4) Researchers don't know exactly what's causing these outbreaks

In both Michigan and Wisconsin, the source of infection is unknown, and health officials aren't sure of how it spread.

This isn't entirely surprising, Chen said, considering researchers don't know exactly how Elizabethkingia anophelis is transmitted. But they suspect people get sick by coming into contact with the bacteria in hospitals or through contaminated water. And, again, they are finding that the bug can be passed from mothers to babies.

"We are looking at many possible sources and have not ruled anything out definitely at this point," said Julie Lund, communications director at Wisconsin's health department, "but we are reasonably certain that groundwater is not the source." The CDC is also helping Wisconsin with testing of samples, including health care products, water sources, and the environment. "To date, none of these have been found to be a source of the bacteria."

5) The bacteria seem to be resistant to antibiotics and disinfectants

Researchers originally suspected antibiotics could be effective against Elizabethkingia, but they're finding these bacteria are actually quite tough. They can resist disinfectants like bleach, and they also seem to be able to outsmart many of the antibiotics we have available.

"Our studies show that Elizabethkingia acquired some antibiotic-resistant genes that we originally thought were not supposed to be there," said Chen. "That means Elizabethkingia are quickly adapting to antibiotics."

For now, Chen said, it's not clear whether the bacteria are more resistant and spreading more quickly, whether we're just better at tracking it, or both.

"Because it's understudied, there's a lot we don't know about Elizabethkingia," Chen explained. Researchers only recently developed testing that allowed them to differentiate among Elizabethkingia species, so the improved detection may be why this bug seems to be popping up more.

But Chen suspects we'll be hearing more about this bacteria as both detection — and, potentially, drug resistance — get stronger.

Update: After publication, Dr. Chen clarified one of his quotes about the age of Elizabethkingia victims.