Mexico has denied responsibility for the nationwide outbreak of a parasitic infection linked to lettuce that has sickened thousands across 41 U.S. states.
Laboratory-confirmed cases of cyclosporiasis, an illness that causes unpleasant symptoms such as explosive diarrhea, surpassed 4,000 as of July 21, according to the Centers for Disease Control and Prevention, with the actual number of sick estimated to be above 10,000. The U.S. Food and Drug Administration linked the outbreak back to lettuce grown by Taylor Farms in the central Mexican state of Guanajuato.
The country’s health minister, David Kershenobich, refuted the FDA’s assertion on July 21. The same day, Health and Human Services Secretary Robert F. Kennedy Jr. said in a news briefing the outbreak was “under control.”
“So far, no evidence has been found to indicate that it originated there,” Kershenobich said in a news conference, per Reuters. “However, we are taking all precautions in case that were the case.”
Kennedy and the Trump administration have faced criticism for cuts to relevant health agencies, with some critics indicating that scaled-back surveillance and limited staffing enabled not only the cyclospora spread, but other recent outbreaks like screwworm. Last year, the CDC scaled back a decades-long federal-state partnership that monitors foodborne illnesses, including those caused by cyclospora.
Still, Kennedy called the critiques “invalid.”
“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,” he said in the July 21 briefing.
Authorities in the United States and Mexico are continuing to search for a cause behind the case clusters, a task that has proven messier than other foodborne outbreaks of the recent past.
What was the ‘false positive’ all about?
Taylor Farms said in a July 19 statement that the FDA had “apologized” to the brand for a “false positive” when testing its iceberg lettuce products from central Mexico for cyclospora. But the company’s statement doesn’t tell the whole story, said food safety expert Bill Marler, as it does little to prove culpability one way or another, something not unusual in such an investigation.
“A positive test means nothing and a negative test means nothing because the product they were testing was not the product people were consuming,” Marler told USA TODAY. “The product that people consumed, the people ate the evidence … or it’s past its best-by date and was thrown out.”
The FDA made a similar point in a July 20 X post, saying, “To clarify, this false-positive lab sample DOES NOT change the basis for FDA’s ongoing outbreak investigation or the overwhelming epidemiological data supporting the current voluntary recall by Taylor Farms.”
Outbreaks are often traced back to manufacturers, growers, or distributors despite food samples that never test positive for a pathogen. When that happens, it’s not because they weren’t the underlying source, said Marler, but because the culprits have already passed through the system or were hiding in other places, like soil or water.
“From 33 years of experience handling these cases, there is, for the most part, never a food product available to test in an outbreak,” he said. “Because by the time you figure out the outbreak is going on, the product is long gone. That’s especially true for perishable products.”
So what does the false positive really mean? Not much either way, said Marler, who also added that Mexico’s arguments of nonculpability are subject to the same uncertainty.
“If it had tested positive, it doesn’t necessarily mean for sure that Taylor Farms was the source,” he said. “And if it tested negative, it doesn’t absolve Taylor Farms of being the cause.”
Source: usatoday.com
