Several cases of diarrheal illnesses in northwest Missouri, possibly caused by Shiga-toxin producing Escherichia coli (STEC) and including at least one confirmed case of E. coli O103 are behind the public health alert issued over the weekend by the Missouri Department of Health and Senior Services (DHSS). According to information contained in the alert, the possible outbreak may be due to consumption of locally produced raw milk and other unpasteurized dairy products. Anyone with the signs or symptoms of STEC infection should seek immediate medical care, DHSS says. It suggests health providers evaluate patients adequately to determine if testing for STEC infections is warranted. Symptoms of STEC infection include severe stomach cramps, diarrhea (which is often bloody), and vomiting. If there is fever, it usually is not very high. Most patients’ symptoms improve within 5–7 days, but some patients go on to develop hemolytic uremic syndrome (HUS), usually about a week after the diarrhea starts. Acute renal damage, microangiopathic hemolytic anemia, and thrombocytopenia are the “triad of findings” that DHSS says add up to HUS. The Missouri health alert continues with advice for those making clinical decisions. It cautions that the use of antibiotics in patients with suspected STEC infections is not recommended until complete diagnostic testing can be performed and STEC infection is ruled out. It says some studies have found that administering antibiotics in patients with STEC infections might increase their risk of developing HUS. If a patient has severe intestinal inflammation and perforation is a concern, antibiotic use may be warranted. The Missouri public health alert includes specific instructions for medical personnel submitting patient stool samples that will be cultured to STEC O157:H7 and simultaneously assayed for non-O157 Shiga toxins. The Missouri State Public Health Laboratory is conducting the tests. Medical providers are required to report within one day any suspected or diagnosed cases of Shiga toxin-producing STEC.