When people think of food safety, they usually picture inspectors in white coats and hairnets walking around a factory floor. That’s certainly part of the process. But detecting and responding to foodborne outbreaks like listeriosis involves an entire hidden infrastructure that most people never see. Right now, that system is being eroded.
Why Is Listeria So Hard to Diagnose?
Let me start with something simple: it’s hard to diagnose Listeria monocytogenes infections. Microbiologists call the bacterium “fastidious.” That means it doesn’t grow easily in the lab, especially not from blood or spinal fluid cultures. In addition, many doctors do not think about even testing for the infection, because the symptoms of fever, headache, diarrhea, and confusion are vague enough to be mistaken for a number of other illnesses. Diagnosis depends on a doctor suspecting the disease, then ordering specialized diagnostic tests.
How Are Listeria Outbreaks Detected and Tracked?
Even when a patient is correctly diagnosed, that’s only the beginning. What turns a case of listeriosis into an outbreak investigation is the public health infrastructure that surrounds clinical medicine.
In the United States, we’re fortunate to have a system called the Listeria Initiative, developed by CDC and other agencies, which requires every confirmed case of listeriosis to be reported and investigated. Epidemiologists interview every patient reported and collect detailed food histories. State laboratories then test the patient’s specimen to perform “”DNA fingerprinting” of the bacteria using techniques like whole genome sequencing.
The DNA fingerprints of Listeria cases are then compared across a national database to identify clusters—cases in different states that may look unrelated until the lab results reveal the patients were infected with the exact same strain. If the strains match, it usually means the patients likely ate the same contaminated food product.
The cases I discussed in my last post—one linked to nutritional shakes for elderly adults, the other to prepackaged sandwiches—only came to light because of this type of careful, labor-intensive work. In both instances, there were long gaps between early cases and later ones. It was only when new patients showed up with genetically identical strains of Listeria that investigators reopened cold cases, reviewed food production and distribution records, and eventually identified the contaminated products. That process can take months, even years.
Why We Still Need People—Not Just Technology
This is not something that artificial intelligence can do automatically. It requires human beings, including highly skilled public health laboratorians, epidemiologists, and food safety investigators, working together across jurisdictions, often with incomplete information and limited resources. It’s the kind of work that gets no attention when it succeeds and becomes the focus of blame when it doesn’t.
Why Public Health Surveillance Is at Risk
This brings me to a growing concern. Many of the systems that allow us to detect outbreaks, including public health labs, food inspection units, CDC epidemiology programs, are being scaled back or threatened with cuts. When budgets are slashed, what disappears first is often the slow, unglamorous work of surveillance: the phone calls to patients, the food history questionnaires, the genetic typing of bacteria, and the cross-matching of data across states. Without these, dangerous outbreaks like the ones I described won’t just be harder to solve. They’ll be harder to even detect in the first place.
So when I hear people say we have the safest food supply in the world, which is largely true, I always add that it only stays that way if we keep investing in the people and systems that keep us safe.
The next time you see a headline about a food recall or a bacterial outbreak, remember that behind it are teams of people doing painstaking work to make connections that most of us would never see.