First implicated in a 1993 U.S. outbreak caused by undercooked ground beef, the Shiga toxin-producing E. coli (STEC) known as O157:H7 has become a familiar term associated with foodborne illness.
High-profile outbreaks—last year’s deadly crisis in Germany, attributed to O104 in sprouts, and another in Japan linked to O111 in raw beef—have significantly raised public awareness of lesser-known pathogenic types of E. coli called non-O157 STEC.
The CDC estimates that out of 265,000 STEC infections in the U.S. annually, 64% are caused by non-O157 STEC. Although infections that progress to severe illness are typically caused by E. coli O157:H7, life-threatening conditions such as hemolytic uremic syndrome (HUS) have been associated with non-O157 STEC.
FoodNet, a CDC surveillance system for tracking illness, began collecting data on non-O157 infections in 2000. Ten years later, the annual number of cases had risen from 57 to 451, due in part to more frequent testing, increased capability, and better reporting.
Until recently, foods implicated in U.S. outbreaks of non-O157 STEC—milk, salad, punch, apple cider, lettuce, berries, cheese, margarine—did not include beef. But in 2010, one major food business ended up recalling 8,500 pounds of ground beef after three people became ill with E. coli O26 infections.
The CDC estimates that six serogroups are responsible for 70% to 83% of non-O157 STEC illnesses. In September, the USDA’s FSIS determined that pathogenic strains of those serogroups—O26, O111, O121, O45, O103, and O145—would be considered adulterants in beef.