A food-safety scare can contaminate a restaurant stock long after the outbreak is over.
That is the risk facing Taco Bell as health officials investigate whether some of its restaurants or ingredients played a role in a broader rise in cyclosporiasis cases -- an infection caused by a parasite that can cause prolonged diarrhea.
The parasite is often spread through contaminated fresh produce. As of July 13, the Centers for Disease Control and Prevention said it had recorded 1,645 domestically acquired cases across 34 states, including 141 hospitalizations.
Investigators are tracing multiple produce items and the locations patients visited before becoming sick. Michigan officials said lettuce or salad greens had emerged as a potential source, although they haven't ruled out other foods or identified a specific product, supplier or restaurant.
Still, Taco Bell said it temporarily removed some ingredients at select restaurants as a precaution. Markets are quick to price in the possibility that an investigation becomes a brand problem and starts affecting sales. Shares of Taco Bell owner Yum! Brands dropped 2.2% on Tuesday following the CDC's report, and have fallen another 2.3% on Wednesday.
If history is any guide, food-safety scares rarely become investment disasters because of one missing topping. They become disasters when customers start questioning the entire kitchen.
Chipotle Mexican Grill offers a painful lesson. When the chain was linked to the E. coli outbreak in 2015, investigators never identified a specific ingredient as the probable source. Chipotle used shared fresh ingredients across much of its menu, which has made it difficult to isolate one source and reassure customers about unaffected items.
The company closed dozens of restaurants in affected regions -- even though they had no reported illnesses -- and introduced a broad overhaul of food-safety procedures. Still, the outbreak had quickly turned into a trust crisis for the brand.
Comparable sales fell 14.6% year over year in the fourth quarter of 2015, and remained nearly 30% down in the following quarter. The stock plunged 47% from its August 2015 peak in the following six months, and didn't fully recover until mid-2019.
In another case, the damage to McDonald's was more contained. In July 2018, salads sold at McDonald's were linked to a Cyclospora outbreak. The company quickly stopped selling salads at roughly 3,000 restaurants, replaced the affected lettuce blend, and changed suppliers. The stock was barely affected and finished the second half of the year 13% higher.
The chain faced a larger scare in October 2024, when an E. coli outbreak was traced to slivered onions served on its Quarter Pounders. McDonald's quickly pulled onions and temporarily removed Quarter Pounders in affected markets. It found an alternate supplier, resumed normal sales within weeks, and the CDC later declared the outbreak over.
McDonald's shares closed down 5.1% on the first full trading day after the initial CDC announcement and remained 11% lower three months later. U.S. comparable sales fell 1.4% year over year in the fourth quarter of 2024 and declined another 3.6% in the first quarter of 2025 as lower-income customers pulled back, partly reflecting impact from the outbreak.
But the damage never approached Chipotle's prolonged collapse. Share prices started picking up again in early 2025 as investors concluded the E. coli damage was temporary and turned their attention to the chain's value deals, which were expected to restore traffic and sales. McDonald's U.S. comparable sales rebounded to 2.5% growth in the second quarter of 2025.
For Yum investors, the early evidence looks closer to McDonald's than Chipotle. No agency has confirmed Taco Bell as the source, and officials are examining ingredients that could be temporarily removed without shutting down the chain's broader menu.
Still, companies cannot control how consumers perceive risk, especially when it comes to food safety. Investors should continue watching how the cyclosporiasis outbreak develops and whether Taco Bell responds well enough to address consumer concerns.
Write to Evie Liu at evie.liu@barrons.com
This content was created by Barron's, which is operated by Dow Jones & Co. Barron's is published independently from Dow Jones Newswires and The Wall Street Journal.
(END) Dow Jones Newswires
July 15, 2026 14:49 ET (18:49 GMT)
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