A severe E. coli outbreak linked to McDonald's Quarter Pounders has resulted in one death and 49 reported illnesses across 10 states, primarily affecting Colorado and Nebraska. The Centers for Disease Control and Prevention (CDC) has highlighted that the outbreak led to ten hospitalizations, including a child with hemolytic uremic syndrome. Investigators are focusing on fresh slivered onions and quarter pound beef patties as potential sources of contamination. In response, McDonald's has proactively removed these ingredients from affected states and temporarily ceased sales of Quarter Pounders in those areas while the investigation continues. The outbreak has caused a significant drop in McDonald's stock prices. People experiencing severe E. coli symptoms after consuming these products are advised to seek medical attention immediately.