America's largest food distributor has stopped buying iceberg lettuce from Mexico as the record U.S. cyclospora outbreak continues to disrupt the nation's food supply.Sysco CEO Kevin Hourican said the company has halted purchases of Mexican-grown iceberg lettuce after the outbreak was linked to lettuce served at Taco Bell restaurants. The U.S. Food and Drug Administration has traced the outbreak to iceberg lettuce supplied by Taylor Farms' operations in central Mexico, while investigators continue examining whether other sources are also involved."We're not buying iceberg lettuce from them, and we're not buying it from Mexico," Hourican said.The move shows how the largest U.S. outbreak of cyclosporiasis on record has forced adjustments to the food supply chain as cases of the disease continue to mount (Getty)He said Sysco is also working to reduce its reliance on any single supplier."To the degree that we can further diversify our procurement, that is something we're actively working on," he said.Sysco suspended sales and distribution of Taylor Farms' Mexican-grown iceberg lettuce in mid-July and issued a voluntary recall before Taylor Farms announced its own recall. While describing Taylor Farms as "a high quality, high integrity shop," Hourican said the company had no choice but to act.The largest cyclospora outbreak has now expanded to include 15 states as federal health officials report more than 10,000 confirmed cases (Getty Images)"We've had to take actions," he said. "We've moved source of product away from them to the degree that we can. Because they're really big, you can't just turn it off overnight."The outbreak has spread beyond a single supplier. Former FDA Commissioner Scott Gottlieb said last week that some major retailers and restaurant chains have begun avoiding produce from other growers in central Mexico amid concerns the contamination could be more widespread.Sysco is now sourcing iceberg lettuce from U.S. growers. Hourican said the company has been able to secure enough supplies, helped in part by lower consumer demand for lettuce following the outbreak.The diarrhea-inducing parasite, linked to shredded iceberg lettuce from mega produce supplier Taylor Farms, has been making thousands of people sick this summer (Getty Images)"Taylor Farms is the largest producer — they're the biggest — and if we're not able to buy from them, we can easily go elsewhere," he said. "Replacing the amount we buy elsewhere is the challenge, and it's something that we're working on."Cyclospora is a microscopic parasite that spreads through food or water contaminated with human feces. The infection typically causes severe diarrhea and other gastrointestinal symptoms. While most people recover, health officials in Michigan have linked two deaths involving people with significant underlying medical conditions to illnesses that may have been worsened by cyclospora-related dehydration.According to the Centers for Disease Control and Prevention, the outbreak has grown to 10,468 laboratory-confirmed cases nationwide, with another 12,255 suspected cases awaiting laboratory confirmation, making it the largest cyclospora outbreak recorded in the United States.