The outbreak has sickened at least 53 people across 16 states. It was originally traced to chopped romaine lettuce grown in Yuma, Arizona, US. However, the CDC recently issued an update that said customers should also avoid whole heads and hearts of romaine, in addition to chopped lettuce, unless they can determine that it was not grown in Yuma.
Consumers are also advised to dispose of any store-bought romaine lettuce they already have at home, as no single grower, brand, or distributor has been implicated in the outbreak.
The CDC said that the investigation is ongoing and that it will provide more information as it becomes available.