The U.S. Centers for Disease Control and Prevention (CDC) announced Monday evening that it is collaborating with public health officials in several states and the U.S. Department of Agriculture’s Food Safety and Inspection Service to investigate a multistate outbreak of Shiga toxin-producing Escherichia coli O157:H7 infections. The likely source of the infections, CDC reported, is the now-recalled ground beef produced by Wolverine Packing Co. of Detroit, MI, and distributed nationwide for retail and restaurant use. On Monday, CDC also released some advice to consumers about avoiding eating undercooked ground beef in restaurants, which is what the people sickened in this outbreak reported doing. Investigators have not released the names of any outbreak-associated restaurants. A total of 11 individuals infected with the outbreak strains of STEC O157:H7 have been reported from four states, CDC noted. The number of ill persons identified in each state is as follows: Massachusetts (1), Michigan (5), Missouri (1) and Ohio (4). Among persons for whom information is available, CDC stated that they became ill with symptoms from April 22, 2014, to May 2, 2014. Those sickened range in age from 19 years to 46 years, with a median age of 26 years. Fifty-four percent of ill persons are male. Among 10 people with available information, six reported being hospitalized. None of those sickened in this outbreak have developed HUS (hemolytic uremic syndrome, a type of kidney failure), and no deaths have been reported, CDC noted. Recent reports of four HUS cases in Kansas, including one woman who had traveled to Texas, have not officially been connected to this CDC outbreak investigation. However, given the wide distribution and the large amount (about 1.8 million pounds) of the now-recalled ground beef, more E. coli cases may emerge. Food Safety News will update this story on Tuesday with comments from CDC officials about the progress of the investigation. According to the CDC report, investigators are using the PulseNet system to identify cases of illness that may be part of this outbreak. PulseNet, the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC, obtains DNA “fingerprints” of E. coli bacteria through diagnostic testing with pulsed-field gel electrophoresis, or PFGE. The type of bacteria responsible for this outbreak is among those referred to as Shiga toxin-producing E. coli, or STEC. Some types of STEC frequently cause severe disease, including bloody diarrhea and hemolytic uremic syndrome (HUS), which is a type of kidney failure. STEC bacteria are divided into serogroups (e.g., O157 or O121). E. coli O157 is the STEC serogroup found most commonly in U.S. patients. Signs and symptoms of E. coli infection are available here. This outbreak can be visually described with a chart showing the number of persons who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that began after May 1, 2014, might not yet be reported due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of two to four weeks. Please see the Timeline for Reporting Cases of E. coli O157 Infection for more details. Epidemiologic and traceback investigations conducted by officials in local, state, and federal public health, agriculture, and regulatory agencies indicate that ground beef produced by Wolverine Packing Co. is the likely source of this outbreak. As of May 16, 2014, in interviews, ill persons answered questions about foods eaten and other exposures during the week before becoming ill. All of the 10 ill persons interviewed reported eating ground beef prepared at a restaurant before becoming ill. Findings of multiple traceback investigations of the ground beef used at restaurants where ill persons reported they had dined identified Wolverine Packing Co. as the source of the ground beef. On May 19, 2014, Wolverine voluntarily recalled approximately 1.8 million pounds of ground beef that may be contaminated with STEC O157:H7. The ground beef was shipped to distributors for retail and restaurant use nationwide. There was no distribution of the products to the Department of Defense, the National School Lunch Program, or catalog/Internet sales. Products are regulated by USDA-FSIS and bear the establishment number “2574B” inside the USDA mark of inspection and have a production date code in the format “Packing Nos: MM DD 14” between “03 31 14” and “04 18 14.” A full list of recalled ground beef products is available from the FSIS website. CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill persons and to interview them about foods eaten before becoming ill. FSIS is continuing to work closely with CDC and state partners during this investigation to determine the source of contamination and identify any other potentially contaminated products still on the market. CDC will update the public when additional information is available.