Seven pathogens tracked by lettuce-watch. Each dossier includes clinical profile, reservoir, typical matrices, underdiagnosis multiplier, and historical outbreak patterns.
Severity: severe (HUS 5–10% of cases)
The dominant STEC serotype in US foodborne outbreaks. Cattle are the primary asymptomatic reservoir. Transmission via ground beef, leafy greens, raw milk, and unpasteurized juice. Infectious dose: as few as 10–100 organisms.
Severity: severe (HUS 2–5% of cases)
The "Big 6" non-O157 serogroups — O26, O45, O103, O111, O121, O145 — declared adulterants in ground beef by USDA-FSIS in 2012. Similar reservoir and transmission to O157:H7.
Severity: moderate–severe
Multiple serotypes tracked: Typhimurium, Newport, Heidelberg, Oranienburg. Reservoir is broad — poultry, eggs, cattle, pigs, reptiles. Common in produce via contaminated irrigation water and in ground beef.
Severity: moderate (prolonged illness if untreated)
A protozoan parasite (not a bacterium). Reservoir is human — no animal host known. Transmission via imported produce, particularly cilantro, raspberries, basil, and lettuce. Annual late-spring/summer outbreaks in the US are linked to imported produce from Mexico and Guatemala.
Severity: moderate
Reservoir is exclusively human. Transmission is fecal-oral — person-to-person, contaminated food/water, or food handled by an infected worker. Infectious dose is very low (10–100 organisms).
Severity: mild–moderate (severe in elderly/immunocompromised)
Leading cause of foodborne illness in the US by case count. Reservoir is human; transmission is person-to-person, contaminated food/water, or leafy greens handled by an infected food worker. Infectious dose is ~18 viral particles.
Severity: severe (mortality 15–20% in vulnerable populations)
Soil- and water-borne. Vulnerable populations (pregnant women, neonates, elderly, immunocompromised) face a 20× elevated risk. Common vehicles include deli meats, soft cheeses, melons, sprouts, and ice cream.
