Most strains of Escherichia coli, or E. coli, are harmless. But some produce toxins that can sicken or kill people. The USDA banned the most commonly identified strain — E. coli O157:H7 — from raw ground beef. It’s scheduled to ban another six strains in June. Here are some outbreaks associated with the those six strains:

E. Coli O26: A multi-state outbreak linked to raw clover sprouts at Jimmy John’s sandwich shops sickened more than two dozen people and hospitalized seven this year. In 2010, Cargill recalled about 8,500 pounds of ground beef because it may have been contaminated with this strain and led to three illnesses in New York and Maine.

E. Coli O45: Through 2008, CDC had identified three outbreaks linked to this strain. Two were suspected to involve infections from contact with animals at a petting zoo and a family farm.

E. Coli O103: In 2000, two people were hospitalized in an outbreak possibly linked to water-based punch at a banquet hall in Washington state.

E. Coli O111: The first community outbreak linked to this strain in the United States sickened five dozen girls attending a Texas cheerleading camp in 1999. More recently, one person was killed in a 2008 outbreak traced to an Oklahoma restaurant; hundreds were sickened. In both cases, the exact source of contamination is unknown.

E. Coli O121: As of 2008, the largest outbreak tied to this strain involved contaminated lettuce that sickened 42 people at a catered event in Utah.

E. Coli O145: Shredded romaine lettuce from an Ohio processing plant was contaminated with this strain and sickened more than two dozen people in 2010. Three developed kidney failure. No deaths have been reported.

Sources: Centers for Disease Control and Prevention, U.S. Department of Agriculture