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The Food and Drug Administration (FDA) expanded its investigation of the Cyclospora outbreak on Wednesday, announcing that there are thousands of confirmed cases across more than a dozen states.

The intestinal illness was first reported in July among people who developed severe diarrhea after eating shredded lettuce at Taco Bell. Health authorities later traced the outbreak to contaminated lettuce supplied to the fast food restaurant by Taylor Farms de Mexico.

"Due to the additional interview data, the outbreak now includes people who reported exposure to Taco Bell or recalled Taylor Farms de Mexico iceberg lettuce," the FDA said in a news release.

According to the FDA, 6,358 cases have now been reported across 15 states. Six states — Arkansas, Iowa, Missouri, Nebraska, New Hampshire and North Carolina — were added since the administration’s previous update on July 24.

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Lettuce crop is watered in a field in Bakersfield, California.

A crop of lettuce is watered in Bakersfield, California, in 2021. (Bloomberg via Getty Images)

The FDA said the outbreak began on June 22, nearly a month before Taylor Farms de Mexico voluntarily recalled all lettuce sourced from central Mexico on July 17.

Since then, Cyclosporiasis has been linked to 278 hospitalizations and two deaths in Michigan, according to the FDA.

"We also expect to continue to see the number of confirmed cases rise, despite the recall, due to the fact that it can take as long as six weeks for CDC and state officials to determine if a sick person is part of this outbreak," the FDA said.

Cyclosporiasis outbreak illustration

A massive surge in Cyclospora cases means people may be mistaking this parasitic foodborne infection for a standard summer stomach bug. (iStock)

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Cyclospora is a single-celled parasite that can cause stomach cramps, nausea, fatigue, weight loss and other health problems, though some infected people remain asymptomatic, according to the U.S. Centers for Disease Control and Prevention (CDC).

Symptoms usually begin about one week after being infected and can last for a few days to a month, according to the CDC. Symptoms can also appear to go away before returning one or more times.

Man sits on a bed and holds his stomach while home alone.

Man sits on a bed and holds his stomach while home alone. Cyclospora can cause stomach cramps, as well as a number of other symptoms. (iStock)

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The FDA again urged consumers and retailers to throw away contaminated lettuce, including Marketside-branded products sold in grocery stores across 27 states in early July.

Health officials also recommend sanitizing any surfaces that came into contact with the lettuce and contacting a doctor if symptoms develop after eating it.