WASHINGTON — Federal health officials have declared the nation’s largest recorded cyclospora outbreak over after the foodborne parasite sickened more than 12,000 people and was linked to two deaths across 21 states. The Centers for Disease Control and Prevention said Friday that infections had dropped significantly and that the shredded iceberg lettuce tied to the outbreak is no longer being sold in stores or served by restaurants. The lettuce was imported from Mexico by Taylor Farms. Cyclospora can cause severe gastrointestinal illness, and public health experts caution that the official case count likely understates the outbreak’s reach because many people do not seek medical treatment for prolonged stomach illness. The outbreak rattled consumers and the fresh-produce industry, prompting changes in buying habits and contributing to losses for domestic lettuce growers. Some producers reportedly plowed crops under as demand weakened, underscoring how quickly a breakdown in food-safety confidence can spread beyond the checkout line. The federal response also drew criticism, including questions about the Trump administration’s handling of the outbreak and the government’s investment in food-safety research. The CDC’s declaration means the immediate outbreak is considered over, not that every food-safety question has been answered. The Food and Drug Administration is continuing its investigation into the lettuce. The agency also reports other ongoing cyclospora outbreaks for which no source has been identified. Taylor Farms said its facility in central Mexico remains closed while the FDA, company investigators and independent experts complete their work. “We will have more information to share at that time,” a company spokesperson said. Consumers should continue following public health guidance on washing produce and seeking medical care for persistent or severe gastrointestinal symptoms. The end of the outbreak removes the contaminated product from the market, but the unfinished investigation leaves regulators facing the harder question: how did the contamination happen, and what will prevent a repeat?