E. Coli Outbreak From Salad Grows as CDC Reports 24 People Infected

Seven more people are now included in an outbreak thought to be linked to salad greens contaminated with a particularly serious strain of E. coli bacteria, the Centers for Disease Control and Prevention announced Wednesday. Public health officials identified new cases in Pennsylvania, California, Maryland, New Jersey and Indiana.

The CDC did whole genome sequencing on the bacteria that caused the outbreak and found they were genetically similar to those implicated in a similar outbreak in Canada. This means it's likely that there's a source of the outbreak that both countries shared, according to a press release issued by the agency when the outbreak was first announced in December.

However, neither Canadian authorities nor the CDC have been able to figure out exactly how people were getting sick; some people ate prepared salads at restaurants, while others likely got sick eating lettuce at home.

E. coli lettuce 2
Farmer Tobias Haack drives a tractor over thousands of heads of lettuce in order to mulch them back into the ground of a field on June 4, 2011, near Hamburg, Germany. Sean Gallup/Getty Images

All 13 of the people interviewed by American public health officials said they'd eaten "leafy greens" in the week before they felt sick; five said they'd eaten romaine lettuce. That particular type of lettuce was the source of the Canadian outbreak, according to the Public Health Agency of Canada. However, the CDC noted that people who got sick during this outbreak "were not more likely than healthy people to have eaten romaine lettuce."

Nevertheless, the short shelf life of salads may mean the outbreak isn't likely to get worse; the people affected got sick in mid-November and early December. Canadian authorities declared their outbreak over on Wednesday. ("More time is needed before CDC can say the outbreak in the United States is over. This investigation is ongoing," the U.S. agency stated in its update.)

E. coli outbreaks happen when people eat or handle food that's got the bacteria on it; that bacteria usually comes from poop excreted by infected animals. The strain of E. coli involved in this outbreak, O157:H7, is particularly serious. In the U.S., nine people were hospitalized due to the infection and two people were diagnosed with a type of kidney failure called hemolytic uremic syndrome.

The fact that lettuce can come into contact with poop at all should really be enough to convince you to always follow safe food handling practices, which include washing your hands regularly and rinsing your fruits and vegetables under running water.