A mysterious cluster of killer bacterial infections is sweeping a US state in an outbreak that has experts baffled: Disease is resistant to most antibiotics
It's thought the rare bloodstream disease known as elizabethkingia anophelis has killed 18 and infected 48 people in Wisconsin since November.
Symptoms include fever, shortness of breath, chills and cellulitis (an infection of the skin and tissues under the skin, most commonly on the lower legs.)
The disease is resistant to some antibiotics, but no one is sure how it's infecting so many people - or why it's proving so deadly.
The Wisconsin department of health is investigating and has alerted healthcare providers, infection experts and laboratories statewide.
"At this time, the source of these infections is unknown and the department is working diligently to contain this outbreak," it said in a statement.
Most of those killed by the disease are over 65, and all patients have a history of at least one serious illness.
Elizabethkingia anophelis was discovered in mosquitoes in 2011 and is associated with meningitis in infants and diseases originating in hospitals, although its transmission route is unclear.
The infection is not spread from person to person, but could potentially come from a food supply or medication system.
Dr William Schaffner, an infectious disease expert at Vanderbilt University Medical Center, told abcnews.go.com:
"Outbreaks of elizabethkingia have been associated with contaminated ventilators or contaminated [injectable] medication or tube feeding, or something like that, and then it gets into the bloodstream." He said the bacteria can be particularly deadly in premature infants, who do not have fully developed immune systems.
The Centers for Disease Control and Prevention (CDC) has sent eight "disease detectives" to Wisconsin to help pinpoint the source of the outbreak, and says its research suggests the infections all stem from one source.
"Our main priority here is to try and find out where this is coming from so that we can prevent additional cases," the CDC's Dr Michael Bell told FOX 6 News.
"Not only is it all elizabethkingia anophelis but it is anophelis species that has the exact genetic fingerprint across several dozen cases, and that's very unusual."
He said elizabethkingia is an environmental organism that is naturally found in dirt and water across the world.
The bacteria was named after the CDC's Elizabeth King, who studied meningitis in infants.
A report released by the CDC last year looked at three cases of the disease in Hong Kong, all at the same hospital.
The first was a 21-day-old baby boy, who was admitted to hospital with a fever in July 2012.
His mother came in a day later with post-partum fever, chills, rigour and abdominal pain.
In November 2012, a 33-year-old pregnant woman stayed in the same cubicle as the mother of that baby, and developed a fever within three days and had to have an emergency caesarean.
Her little girl was "pale and flaccid" at birth and had to have CPR, before developing jaundice and an intestinal disease that is a common cause of mortality in premature babies.
It may provide some clues to what's happening in Wisconsin, where the race is on to find the answer to this deadly riddle.