In the May of 2023, a significant increase in Cyclospora cases associated with a Mexican-style restaurant in Limestone County, Alabama was investigated by the Alabama Department of Public Health. An outbreak investigation was initiated on June 7, 2023. A case control study was launched on June 12. Exposures were reported between May 20 and June 6, 2023.

A case was defined as a person who ate food from the restaurant between May 20 and June 6 and developed diarrhea 2-14 days after their meal was consumed. Those who met the case definition were further divided into two groups: with laboratory confirmation and without laboratory confirmation. A case with laboratory confirmation was a case who had laboratory evidence of Ccayetanensis by polymerase chain reaction (PCR). A case without laboratory confirmation was a case who became ill but lacked laboratory evidence of infection. A control was defined as a person who ate at the restaurant between May 20 and June 6 and did not become ill.

Seventy-one cyclosporiasis cases reported eating at the same restaurant prior to becoming ill. Of those who met the case definition, 38 (81%) were classified as laboratory confirmed, and 9 (19%) were without laboratory confirmation. The primary symptoms reported were diarrhea (100%), fatigue (91%), nausea (81%), and abdominal cramps (74%). 

The only food item statistically significantly associated with illness in univariate analysis was salsa roja, with an OR of 20.5 (95% CI: 3.9, 145.0; p-value: 0.0006), meaning persons that consumed the salsa roja had more than 20 times increased odds of becoming ill. When breaking the food items down by ingredient, there were four ingredients statistically significantly associated with illness in univariate analysis: cilantro (OR: 27.7; 95% CI: 5.3, 283.9; p-value: 0.0009), jalapeños (OR: 27.7; 95% CI: 5.3, 283.9; p-value: 0.0009), onions (OR: 22.2; 95% CI: 4.2, 227.1; p-value: 0.0021), and tomatoes (OR: 8; 95% CI: 1.7, 49.2; p-value: 0.0177). When using backward stepwise logistic regression, only cilantro remained significantly associated with illness (OR: 40.9; 95% CI: 6.4, 808.6; p-value=0.0009).

Confirmed positive specimens were forwarded to the Centers for Disease Control and Prevention (CDC) to be further characterized by genotyping. There were 58 specimens forwarded to CDC for Cyclospora genotyping. However, 10 (17%) specimens failed to result with enough sequence to be included in analysis. Of the 48 specimens successfully genotyped, 34 (71%) were assigned to 2023_012, 4 (8%) were assigned to 2023_015, 3 (6%) were assigned to 2023_069, 2 (4%) were assigned to 2023_002, and 1 (2%) each to 2023_024 and 2023_041. With nearly three-quarters of specimens assigned to the same TGC Code, it suggests that most of the genotyped cases were closely related and likely shared exposure to the same contaminated food. 

The ADPH Bureau of Environmental Services (BES) conducted an environmental assessment on June 9 to identify potential contributing factors that may have played a role in the outbreak. Proliferation factors typically observed in bacterial and fungal outbreaks were not examined as closely since the etiology was known to be parasitic at the time of assessment. Based on the environmentalists’ observations at the restaurant, there were no significant errors in food handling, preparation, and cooking identified. 

A food flow was developed for those menu items most reported by cases identified early in the investigation, including salsa roja, taco salad, queso, guacamole, chicken soup, pico de gallo, and salsa verde; all used fresh, uncooked produce in their recipe. Since imported cilantro has a longstanding history of being a known food vehicle for Ccayetanensis contamination, BES also verified which menu items contained cilantro, as it was not clearly stated on the menu for all dishes. Invoices for fresh produce received between May 25 and June 5 were obtained and shared with ADPH’s federal partners, including the CDC and FDA Core Response Team 4, on June 16. Subsequently, those invoices were shared with Georgia Departments of Public Health and Agriculture on July 10.

Traceback of a cilantro distributor in Texas was conducted. When the Georgia Department of Health communicated their findings about the distributor with colleagues in Texas (TX RRT), neither Texas Department of State Health Services, nor Texas Department of Agriculture had any documentation this firm had ever received a food manufacturing license in their state. TX RRT used the phone and address listed on the invoice provided by the distributor to establish contact with the owner. The operating address for this firm was a residential address located less than five miles from the Mexico border. Records obtained by TX RRT shows that the cilantro was purchased from an import/export firm (Distributor X) located in State of Tamaulipas, Mexico, and held in cold storage in Texas prior to the sale to other firms across the United States. Unfortunately, TX RRT was not able to determine where the cilantro was grown in Mexico.Based upon epidemiology, laboratory, environmental health, and traceback evidence, it is strongly suspected that this outbreak of cyclosporiasis among patrons of a Mexican-style restaurant in Limestone County, Alabama, was linked to contaminated cilantro imported from Mexico. Cilantro imported from Mexico has been identified as a food vehicle in numerous Cyclospora outbreaks in the U.S. over the last nearly three decades.