Don’t eat any romaine lettuce from California’s Salinas Valley because of potential contamination, CDC warns
The Centers for Disease Control and Prevention said romaine lettuce from the Salinas Valley, one of California’s major agricultural regions, may be contaminated with a dangerous type of E. coli bacteria that has sickened 40 people in 16 states.
Most romaine lettuce products are labeled with a harvest location showing where they were grown.

Sorry, I'm paywalled from the Washington Post, but this is really all you need to know.