US salad chains including Chopt, Panera Bread and Sweetgreen have seen a fall in customer visits amid growing public fear of a large cyclospora outbreak linked to possible lettuce contamination. Although none of these chains has been formally connected to the outbreak, anxiety over the parasite, which causes severe gastrointestinal illness, has driven shoppers towards fast-food alternatives instead, while investors have also reacted with sharp share price falls for affected companies.

Placer.ai data shows Chopt's foot traffic fell 7.1 percent and Panera Bread's fell 7.4 percent on 11 July compared with average Sunday figures, while Sweetgreen dropped 3.1 percent; over the same period, traditional fast-food chains such as McDonald's and Wendy's saw a slight rise in custom. The outbreak has reportedly sickened almost 7,000 people according to the US Centers for Disease Control and Prevention, with Michigan the worst-hit state at over 4,300 cases. Sweetgreen's shares have fallen 23.3 percent over five days, while Taco Bell, whose parent company Yum Brands is under scrutiny as a possible source after removing certain ingredients from some Detroit-area menus, has seen its share price drop 7.2 percent and traffic fall correspondingly. Despite the anxiety, some customers, particularly in lower-case areas like New York, remain unaware of or unconcerned by the outbreak.