The cyclosporiasis outbreak that has sickened thousands of Americans is “under control,” according to Health Secretary Robert F. Kennedy Jr. Almost everyone else involved in investigating it is using considerably more hedged language.

Mexico says its own inquiry hasn’t confirmed the source. The FDA commissioner stopped short of Kennedy’s certainty. Michigan health officials, dealing with the largest case count in the country, say the culprit hasn’t been definitively identified at all.

That gap between the confidence at the top and the caution everywhere else is the real story here.

What the FDA Has Linked So Far

The Food and Drug Administration has tied the outbreak, which primarily causes severe diarrhea, to shredded iceberg lettuce processed at a Taylor Farms facility in central Mexico.

Kennedy described the investigation as conclusive.

“We have done extensive forensics, epidemiological forensics, and we’ve identified the source of the outbreak,” he said Tuesday.

FDA Commissioner Kyle Diamantas chose different words. Speaking to Fox News the same day, he said the data strongly supports Taylor Farms as the responsible party. Strongly supports is not the same as identified.

On a media call Monday, Diamantas noted that new cases connected to the outbreak had surfaced as recently as last week, which he said made action urgent to keep contaminated product off shelves.

Mexico Pushes Back

Mexican Health Secretary David Kershenobich said at a news conference Tuesday that his country’s investigation had turned up no evidence the outbreak originated at the facility in question.

That’s a direct disagreement between two governments over the same set of facts, and it isn’t likely to resolve quickly.

Why Cyclospora Is So Hard to Pin Down

The disagreement makes more sense once you understand the parasite involved.

Cyclospora is notoriously difficult to trace. Detecting it in food requires highly sensitive testing. Worse, people often fall ill weeks after eating a contaminated product, which means that by the time investigators recognize an outbreak, the suspect food is typically long since eaten or thrown out.

Investigators therefore lean heavily on epidemiology rather than laboratory confirmation. They map who got sick, when, and what they ate. A positive test result is helpful but not strictly required to identify a source.

That methodology can produce accurate answers. It can also produce answers that another government, applying its own standards, declines to accept.

No Positive Samples, and One False Alarm

To date, no samples from the Taylor Farms facility in Mexico have tested positive for cyclospora.

There was one apparent hit over the weekend. It turned out to be a false positive.

An FDA official explained that the agency moved fast to publicize the result because the sample fell outside the voluntary recall, making it appear to carry urgent public health implications. Subsequent quality checks by FDA laboratory staff showed the result was an error.

Keith Schneider, a food safety professor at the University of Florida, said testing at this stage almost certainly extends well beyond the lettuce itself.

“They may be testing irrigation water. They may be testing soil samples. They may be testing workers associated with that single field or those several fields that would have supplied that product to those locations at that time,” he said.

The Recall and Where the Lettuce Went

Taylor Farms voluntarily recalled all iceberg lettuce grown and processed in central Mexico on Friday, describing the decision as an abundance of caution. The company has also stopped sourcing iceberg lettuce from central Mexico for the remainder of the growing season.

The recalled product reached:

• Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia
• Selected Walmart stores nationwide under the Marketside brand

Michigan’s Numbers, and Michigan’s Caveat

The Michigan Department of Health and Human Services has counted 6,571 cases in the state as of Tuesday, making it the epicenter of the outbreak.

The department’s own website carries language that sits uneasily beside Kennedy’s statement. Officials there say other food items cannot be ruled out, and that no specific type of produce, grower, or supplier has been identified as the source.

That’s a state health agency with the most cases in the country declining to name a culprit while the federal health secretary declares the matter settled.

The Surveillance Fight

Running underneath all of this is a dispute about whether the country can even see outbreaks clearly anymore.

A year ago, the CDC informed 10 states that they were no longer required to actively monitor for cyclospora through FoodNet, a program that helps track how common foodborne illnesses are outside of active outbreaks.

Kennedy rejected the criticism that reduced monitoring has hampered the response.

“Those criticisms are invalid. We’ve had no cuts in our surveillance program,” he said. “We did cuts in the FoodNet program, but they were for redundant surveillance, and all the states will tell you that we’re still doing forensics. We’re still doing surveillance in all the states.”

Several state health departments confirmed to reporters that they continue reporting cyclosporiasis cases to the CDC when local health departments or laboratories detect them.

The concern from food safety researchers is about what passive reporting misses.

“What we’ve been doing is pulling pieces out of the puzzle, and it’s going to make it really hard for us to figure out what the cause of this outbreak is,” said Barbara Kowalcyk, director of the Institute for Food Safety and Nutrition Security at George Washington University. She added that the loss of context makes it harder to understand how a given outbreak fits into longer-term trends.

Reading the Situation

Several things can be true simultaneously, and probably are.

The epidemiological evidence pointing toward the Taylor Farms product may well be strong, since that’s how most produce outbreaks get solved. At the same time, the absence of a confirmed positive sample gives Mexico legitimate grounds to withhold agreement, and the false positive did nothing to strengthen the FDA’s credibility on the point.

Meanwhile, cases were still being identified as of last week, which sits awkwardly with the phrase “under control.”

For consumers, the practical guidance is unchanged and simple. Check whether recalled Marketside iceberg lettuce is in the refrigerator and discard it. Anyone experiencing prolonged severe diarrhea, especially after eating at the named locations, should contact a doctor, since cyclosporiasis is treatable with specific antibiotics but does not typically clear on its own quickly.

The larger question is whether the country’s ability to detect the next outbreak has been quietly diminished. That argument will outlast this lettuce.