3.2 The Big Six Pathogens

Why the Food Code singles out six pathogens

The FDA Food Code does not rank every microbe by how often it appears in outbreak tables. It identifies six organisms that are highly infectious and readily spread from an infected food employee to food, then to guests. Those six are the Big Six: Norovirus, Hepatitis A virus, Shigella spp., Shiga toxin-producing Escherichia coli (STEC), Salmonella Typhi, and nontyphoidal Salmonella.

A diagnosis of any Big Six illness is a reportable event. The employee tells the person in charge. The person in charge notifies the regulatory authority when the Food Code requires it and applies exclusion or, in narrower cases, restriction. Exclusion means the worker does not work in the establishment. Restriction means the worker may be on site but cannot handle exposed food, clean equipment, utensils, or linens. High-risk operations — nursing homes, hospitals, day care, and similar settings serving highly susceptible populations — push more of these cases toward exclusion. Return-to-work criteria are a later chapter. This chapter is about knowing which organisms trigger that machinery and why a manager cannot treat them like a routine stomach bug.

The Big Six are not “the only pathogens that matter.” They are the pathogens that turn employee health into a legal control point. A cook with Staphylococcus aureus on the skin can still create a toxin problem, and Listeria in a walk-in can still devastate a pregnant guest. Those organisms are simply not the six that the Food Code names for diagnosis reporting and default exclusion.

The Big Six at a glance

Memorize the six names as a closed list. If an option adds Listeria, Campylobacter, Clostridium perfringens, Bacillus cereus, or Staphylococcus aureus, it is not a Big Six list — even when the organism is a real kitchen hazard.

The two viruses on the list

Norovirus

Norovirus is the leading cause of foodborne illness in the United States and the organism most likely to close a restaurant after a wedding buffet. It does not grow in the potato salad. An infected employee, an unclean restroom, a vomit incident in the dining room, or shellfish from sewage-contaminated water puts virus particles onto ready-to-eat food. The infectious dose is tiny. Vomiting is projectile and contaminates surfaces far from the original mess. Diarrhea, nausea, and abdominal cramps complete the picture. People can shed virus before they feel sick and after they feel better, which is why exclusion and a strict return-to-work rule exist.

Prevention is almost entirely about people and surfaces: wash hands after the restroom and before handling RTE food, ban bare-hand contact with RTE food, exclude employees with vomiting or diarrhea, clean vomit with the operation’s bodily-fluid procedure, and buy shellfish from approved waters. Cooking helps some foods but is not the control you rely on for a plated salad.

Hepatitis A virus

Hepatitis A is also fecal-oral and also travels on RTE food, produce, ice, and shellfish. The illness is slower and more systemic: fever, fatigue, nausea, abdominal pain, dark urine, and jaundice — yellowing of the skin and eyes. Jaundice is the exam’s brightest flare. A food employee with jaundice is treated as a Hepatitis A case until a medical evaluation and the regulatory authority say otherwise. Do not send a jaundiced cook to the dish pit “just for today.” Exclude and notify.

Hepatitis A can be shed before jaundice appears, so handwashing and no bare-hand contact with RTE food are still the daily controls even when nobody looks yellow. Approved shellfish and produce suppliers matter because water contaminated with sewage is a classic vehicle.

The four bacteria on the list

Shigella spp.

Shigella is a human-reservoir organism. It leaves an infected person in feces, survives on hands, and rides onto salads, sandwiches, and any food touched after cooking. Flies that travel from feces to food are a documented transfer route, which is why pest control is part of the Shigella story and not a separate “facilities only” topic. Hallmark illness is bloody diarrhea with cramps and often fever. The infectious dose is low. Control is handwashing, exclusion of symptomatic or diagnosed employees, potable water, and keeping flies off prep areas. Cooking a burger to 155°F does not fix a cooked chicken salad mixed with bare hands.

Shiga toxin-producing E. coli (STEC)

STEC, including the well-known O157:H7 group, lives in the intestines of cattle and other ruminants and also moves through human feces. The two food stories the exam loves are undercooked ground beef and contaminated produce (lettuce, sprouts, unpasteurized juice). Grinding spreads surface contamination through the patty, so the center of a burger is not “clean until you cook it.” Bloody diarrhea is the hallmark. A subset of guests, especially children, can progress to hemolytic uremic syndrome and kidney failure. That severity is why STEC is Big Six and why a manager does not treat “a little pink in the burger” as a preference when the item is not under a consumer advisory.

Prevention: cook ground beef to the Food Code comminuted-meat standard (155°F for 17 seconds, or an equivalent), prevent cross-contamination from raw beef to RTE food, use approved produce suppliers, exclude employees with diarrhea or a STEC diagnosis, and keep bare hands off RTE food.

Salmonella Typhi

Salmonella Typhi causes typhoid fever. Its reservoir is humans only. There is no “cook the chicken thoroughly” origin story. An infected person or a chronic carrier contaminates food or water with feces. RTE foods and beverages handled by that person are the vehicles. Illness is systemic: prolonged high fever, weakness, abdominal pain, headache, and sometimes a rash. Because carriers can shed the organism without looking acutely ill, a diagnosis is an automatic exclusion-and-report event, not a “wait and see if the fever breaks.”

Nontyphoidal Salmonella

Nontyphoidal Salmonella (NTS) is a different organism group and a different kitchen story. It lives in the intestines of poultry, cattle, pigs, reptiles, and other animals, and it contaminates chicken, turkey, eggs, meat, produce, and unpasteurized dairy. Cross-contamination from a raw chicken cutting board to a salad is the textbook route. Illness is diarrhea, fever, and abdominal cramps, usually within about 6 to 72 hours. Control is cooking (poultry to 165°F), separating raw animal foods from RTE foods, refrigerating eggs and meat, excluding a diagnosed employee, and never washing raw chicken in a way that splashes the sink.

The exam trap is mixing the two salmonellae. Typhi = humans only, typhoid, RTE food and water. NTS = animals and produce, poultry and eggs, ordinary salmonellosis. Both are Big Six. Their controls overlap on handwashing and exclusion, then diverge on cooking and animal-food handling.

Hallmark symptoms the PIC must act on

Employee-health rules later in the guide turn symptoms into actions. Learn the diagnostic clues now so those later rules have a pathogen attached.

Vomiting and diarrhea are exclusion symptoms even before a laboratory name arrives. The Big Six matter when a diagnosis does arrive, when jaundice appears, and when you are choosing prevention that matches the organism.

What is not Big Six — and why the exam asks

Several famous organisms live in nearby sections and in real kitchens. They are not Big Six:

• Listeria monocytogenes grows in the refrigerator and targets deli meats, soft cheeses, and pregnant guests.
• Campylobacter is a leading bacterial cause of illness from undercooked poultry and unpasteurized milk.
• Clostridium perfringens and Bacillus cereus are the sporeformers from Section 3.1.
• Staphylococcus aureus makes a heat-stable toxin after a food handler’s skin or nose contaminates TCS food left in the TDZ.

Those organisms still require controls. They do not, by themselves, create the Food Code’s named diagnosis-reporting list. The cleanest exam trap in this chapter is “Staphylococcus aureus is Big Six because it comes from food handlers.” It comes from food handlers. It is not Big Six. Norovirus is a virus and is Big Six. Do not let “bacteria only” thinking delete the two viruses.

Prevention that covers the whole list is deliberately boring: wash hands, exclude the sick, keep bare hands off RTE food, cook animal foods to the Food Code temperatures, buy from approved suppliers, use potable water and approved shellfish, and control flies. Fancy equipment does not replace those six habits.