McDonald's U.S. sales declined in the fourth quarter of 2024 following an E. coli outbreak linked to its Quarter Pounder hamburgers.The fast-food giant reported on Monday a 1.4 percent drop in U.S. same-store sales, reflecting a shift in consumer sentiment amid health concerns. The outbreak, which sickened over 100 people across 14 states, including 34 hospitalizations and one fatality, led to lawsuits and a decline in foot traffic at its restaurants.Why It MattersThe downturn in McDonald's domestic sales underscores the significant impact of foodborne illness outbreaks on consumer trust and business performance. While the company has been adjusting pricing strategies to combat slowing sales, the food safety issue added to its challenges.What To KnowDespite a decline in U.S. sales, McDonald's international performance helped offset some of the damage. The company reported a 4.1 percent increase in same-store sales in its licensed markets abroad, particularly in the Middle East and Japan, where sales had struggled in recent years.Overall, global same-store sales rose nearly 1 percent for the quarter, surpassing Wall Street's projected 1.1 percent decline, according to FactSet. However, McDonald's revenue fell slightly to $6.38 billion, missing analyst expectations of $6.45 billion. Net income dropped 1 percent to $2.01 billion, with adjusted earnings per share of $2.83, slightly below the predicted $2.85 per share.McDonald's value perception among price-conscious consumers had already weakened earlier in the year due to menu price increases. The company had attempted to counteract this by launching a $5 value meal in June, which successfully drove traffic through December. However, the E. coli outbreak, first reported on October 22, disrupted this momentum.The U.S. Food and Drug Administration (FDA) traced the outbreak to raw onions supplied by California-based Taylor Farms. The investigation, conducted alongside the U.S. Centers for Disease Control and Prevention (CDC) and state health departments, concluded in December after McDonald's removed the contaminated onions from its supply chain.McDonald's responded by intensifying its marketing efforts and revising its pricing strategy to win back consumers. The company invested $100 million in advertising during the quarter, according to CNN, and introduced the new "McValue" menu in January to regain customer confidence.What People Are SayingMcDonald's chairman and CEO Chris Kempczinski, in a statement alongside Monday's earnings report, said: "Accelerating the Arches continues to be the right strategy as we focus on growing market share. We're playing to win, focusing on our customers with outstanding value, exciting menu innovation and culturally relevant marketing."What Happens Next?Investors are watching to see if the brand can recover momentum in its U.S. market, where consumer spending patterns remain volatile. Meanwhile, global expansion and international sales growth provide a potential buffer against domestic headwinds.McDonald's shares rose more than 3 percent at one point in premarket trading on Monday. Markets open at 9:30 a.m. ET.This article contains reporting by the Associated Press