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eat them raw can become infected.” He paused. “However, it’s unusual for
Vibrio
parahaemolyticus
to enter the bloodstream.” He pointed to the slide. “Yet here we see
all
victims had that pathogen in their blood.”
    “With XK59 slicing and dicing blood vessels in the gut and elsewhere, I’m not surprised the bacteria entered their blood,” I said.
    “And the second organism?” Kosta asked, sliding a pale hand forward along the table.
    Muñoz approached him tenderly.
    “Yes,
Aeromonas hydrophila
.” Muñoz paced along the side of the table in professorial style. “Like
Vibrio parahaemolyticus
, this bacterium is a denizen of the sea, but debate exists as to its ability to cause diarrhea in humans. If you search the literature, you will find reports that describe gastrointestinal symptoms linked to this organism in persons who consumed raw oysters.”
    “Hold on!” McCloskey bellowed. “Are you saying
oysters
caused the XK59 poisonings?” He seemed affronted by the notion.
    Muñoz donned a coy look. “To answer that question, we need to discuss a tool epidemiologists often use to study illness outbreaks. It’s called a ‘case-control study.’ It compares exposures among persons with the disease of interest—‘cases’—to others without the disease, or ‘controls.’ The goal of case-control studies is to identify one or more exposures reported more commonly among ill than well persons and thereby identify a likely cause of illness. During the past week, I conducted such a study by interviewing the twelve cases or their next of kin along with a group of persons without XK59 poisoning. I just completed the analysis today.”
    “Who were the controls?” Shaker asked.
    “Individuals in neighborhoods where the cases resided. I identified two controls for each case.”
    Whispering into my ear, Flagstaff said, “He used his CDC affiliation, saying nothing about the UNIT.”
    The next slide showed the dozen cases and 24 controls to be similar in age, race, ethnicity, education level, recent travel history, and presence of underlying medical conditions.
    “What I did next was get a diet history from cases and controls,” Muñoz continued. “I asked cases what they ate during the week before they fell ill and controls what they ate during the week before the interview. To refresh memories, I had subjects consult a calendar. Here’s what I found.”

    “As you can see from the asterisks, the only statistically significant difference was cases were more likely than controls to have eaten seafood.” He scanned the room. “Are we together?”
    Heads nodded with the lone exception of McCloskey who sat stoically with a look of defiance.
    “Seafood is a large category,” he said. “Did you narrow it down?”
    Muñoz advanced the slide.

    “
Shrimp
?” McCloskey erupted. “Are you saying
shrimp
caused the XK59 poisonings?” He raked his eyes over Muñoz as if the Peruvian were a traitor for maligning a major seafood product harvested from his home state of Louisiana.
    Muñoz, feeling the heat, deferred to Bird.
    “Indeed, sir,” Bird said, his voice subdued. “We obtained a sample of leftover shrimp from one of the victims and it yielded
Vibrio parahaemolyticus
,
Aeromonas hydrophila
, and XK59.”
    “Was the shrimp cooked that you tested?” I asked, incredulous that XK59 was present.
    “No, it was raw. It was a portion the victim had refrigerated before barbecuing the rest.”
    “But cooking should have killed the bacteria,” Shaker insisted.
    “And denatured XK59,” I added. “The protein is heat-sensitive.”
    “That’s the problem,” Muñoz riposted. “The victim didn’t barbecue the shrimp thoroughly. Which raises a key point: All of the victims ate shrimp that was outright raw—at sushi bars, for example—or only partially cooked.”
    “How much XK59 was in the shrimp you tested?” I asked Bird.
    “The results are pending.”
    Kosta: “I don’t understand how the shrimp