Lettuce prices rose sharply in the first half of 2026 due to hot weather in Arizona, where about one-third of America’s lettuce is grown. Now, restaurants are dealing with the fallout from a cyclospora outbreak linked to shredded lettuce that has sickened thousands of Americans.

Yum Brands, the parent company of Taco Bell, said Thursday that Taco Bell’s same-store sales are down 2% so far in the July-September period due to customers’ concerns over the outbreak. That compares to a 7% same-store sales increase in the April-June period.

Federal health officials first tied the diarrhea-causing outbreak to shredded iceberg lettuce served at Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio and West Virginia. Later, the U.S. Food and Drug Administration said customers in Illinois, Kansas, Oklahoma and Pennsylvania were also affected.

Taco Bell removed shredded iceberg lettuce supplied by Taylor Farms from its U.S. restaurants on July 17. The following day, Taylor Farms recalled iceberg lettuce grown in central Mexico.

Taco Bell’s sales bottomed out the weekend of July 18-19 but have been steadily improving since then, Yum Brands Chief Financial Officer Ranjith Roy said Thursday in a conference call with investors. Over the last four days, Taco Bell’s U.S. sales have climbed halfway back to their year-ago level, he said.

Yum Brands CEO Chris Turner said Taco Bell’s quick action to contain the issue and its clear communication on social media helped bring diners back. The brand also enticed fans with daily specials like $1 Mexican pizza.

“With respect to the consumer sentiment, we’ve seen real improvement as consumers have understood better the nature of the issue,” Turner said. “They understand that it is not a Taco Bell specific issue.”

Yum Brands shares rose 6% in morning trading Thursday.

Other chains are also feeling some impact from the outbreak even though they haven’t been named in government investigations. Chipotle Mexican Grill said Wednesday that it expects its same-store sales to rise only 1% in the July-September period because of lower traffic due to the outbreak. It had previously expected same-store sales to rise 3% in that period.

Foot traffic at Chopt, a salad-focused chain with 105 locations, was down 12% as of July 23, according to Placer.ai. M Science, another market research firm, found that weekly spending at the salad chain Sweetgreen dropped 10 percentage points compared to last year during the first half of July.

Chopt didn’t respond to a request for comment from The Associated Press. Sweetgreen, which has 285 U.S. locations, did not confirm a drop in sales and said in a statement that its food hasn’t been connected to the current cyclospora outbreak.

“We follow rigorous food safety standards and can trace our ingredients from restaurant to farm,” the company said.

Cyclospora cases have continued to grow. Last week, federal health officials began investigating a new outbreak involving 72 people. As the FDA investigation progresses, officials should get a better understanding of which illnesses are connected and “how complex this outbreak actually has become,” said Craig Hedberg, a food safety researcher at the University of Minnesota.

The outbreak came on top of an already difficult year for the lettuce industry and people who love eating salads. The retail price of a pound of iceberg lettuce jumped nearly 20% between January and June of this year, according to government data. Consumers paid an average of 33% more last month for all fresh lettuce compared to a year earlier, the U.S. Department of Agriculture said.

Lettuce prices advertised by major grocery stores last week averaged $1.86 for a head of iceberg, 25 cents more than the same week a year earlier, according to the USDA. A head of red leaf lettuce cost 52 cents more at $1.66, and a bunch of romaine had an advertised price of $2.49, which was $1.55 higher, the department reported.

Shoppers caught a break with some types of salad mixes, though, which stores advertised at prices 7 to 24 cents cheaper than a year prior, the USDA said.

Elizabeth Canales, an associate professor of agricultural economics at Mississippi State University, said unusually hot weather in Arizona early in the year caused crops to mature too early. That caused big supply gaps until California production began in late April.

Fuel costs, which increased after the U.S. and Israel launched strikes on Iran and Iran blocked most oil tankers from leaving the Persian Gulf, have also been an issue, according to Canales. Lettuce is especially perishable and requires energy for cooling from the time it’s picked to the time it’s sold, Canales said.

“The cold chain needs to be maintained. Cooling and transporting it is very important,” Canales said.

Lettuce has been linked to multiple food poisoning outbreaks in the past, including two in 2018 involving E. coli linked to romaine lettuce grown in Arizona and California.

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Associated Press Writer Mike Stobbe contributed from New York.