A savage strain of E. coli spread on romaine lettuce has killed its first victim in an outbreak that now grips 25 states, sickening a total of 121 people.

The California Department of Public Health confirmed to Ars that a resident had died from an illness linked to contaminated romaine lettuce grown in the Yuma region. “Due to patient privacy laws, we cannot provide further details,” the department said in a statement. But it added that the death was among 24 cases of illnesses in the state linked to the salad staple.

The Yuma region produces the lion’s share of romaine lettuce and other leafy greens for the whole of the US during the winter months. Production shifts northward to California’s Central and Salinas Valleys in March to early April. Therefore, the lettuce you see on grocery store shelves now is likely not from Yuma, and new reports of cases are likely due to reporting lags.

Still, the Centers for Disease Control and Prevention recommends that consumers toss all romaine lettuce unless you can confirm that it didn’t come from Yuma. The same goes for restaurants, and the caution applies to all romaine—chopped, whole, baby, organic, or snippets in mixes. “If you do not know whether lettuce is romaine, do not eat it,” the agency warns. And sadly, most lettuce packaging does not list the specific growing region.

The excessive precaution from the agency is in part due to the particularly nasty strain of E. coli behind the outbreak, which began felling greens-eaters in mid-March. It’s caused by a Shiga toxin-producing Escherichia coli O157:H7 that produces only Shiga toxin type 2 (Stx2)—the more dangerous of the two toxin types. While both (Stx1 and Stx2) are toxic to cells and able to shut down the cell’s protein production, leading to cell death and immune responses, Stx2 is more often associated with severe disease. This includes hemolytic uremic syndrome, or HUS, which destroys red blood cells and damages the kidneys, leading to acute kidney failure.

So far, 14 people affected by the outbreak have developed HUS—but the CDC only has health data on 102 of the 121 people affected by the outbreak. Of those 102, 52 (or 51 percent) have been hospitalized.

Last week, the CDC and the FDA traced illnesses in eight people in a correctional facility in Alaska to whole-head romaine grown at one specific producer, Harrison Farms in the Yuma region. That farm’s growing season had already ended and its fields are now growing grass, health officials reported. Officials are still investigating if other farms, distributors, or sources of contamination are involved.

Shiga toxin-producing Escherichia coli are primarily found in the guts of cattle, but they can also come from pigs and other animals. They are spread via feces. For example, lettuces—or any other produce—can become contaminated if irrigation water becomes contaminated with runoff from cattle farms upstream.