The Center for Disease Control and Prevention (CDC) has issued a stern warning not to eat romaine lettuce—or any lettuce whatsoever, unless it’s clearly not from Arizona—as a serious E. coli outbreak has poisoned over 50 people.

According to NBC News, while nobody has died, 31 people were hospitalized with five people facing a serious E. Coli-related infection called hemolytic uremic syndrome. It was the recent spread of infection to Alaska that urged CDC officials to take note, with infections now being reported in 16 states.

“Based on new information from Alaska, CDC is expanding its warning to cover all types of romaine lettuce from the Yuma, Arizona growing region,” said the CDC. “This warning now includes whole heads and hearts of romaine lettuce, in addition to chopped romaine salads and salad mixes containing romaine.” 

The CDC says that it doesn't have the figures of affected Alaskans yet and also hasn't ascertained just where this contaminated lettuce is coming from. “No common grower, supplier, distributor, or brand has been identified at this time,” it said. Naturally, the easiest solution for everyone right now is simple: don’t risk it, and avoid any kind of lettuce for the time being.

“People who have store-bought romaine lettuce at home, including whole heads and hearts of romaine, chopped romaine, and salads and salad mixes containing romaine lettuce, should not eat it and should throw it away, even if some of it was eaten and no one has gotten sick,” said the CDC. “If you do not know if the lettuce is romaine, do not eat it and throw it away,” it said, simplifying the decision for everyone. The organization also urged consumers to ask businesses “about the source of their romaine lettuce,” and verify it doesn't hail “from the Yuma, Arizona growing region.” 

As for the CDC’s process of deducing the common salad denominator here, the organization logically arrived at its conclusion. “Most people reported eating a salad at a restaurant, and romaine lettuce was the only common ingredient identified among the salads eaten,” said the CDC. “The restaurants reported using bagged, chopped romaine lettuce to make salads.” 

Unfortunately, as NBC News reports, it can take several weeks to locate ground zero of a food poisoning epidemic. A lot of food is shipped to plants where it’s mixed, processed, and packaged together with other food from all kinds of farms, across the country. It’s then redistributed, with the actual source being extremely difficult to determine. As for the physical symptoms of E. coli, they include painful stomach cramps, bloody diarrhea, and vomiting. The bacterial disease is spread through water, animal droppings, or undercooked beef. Stay healthy, everyone—don’t eat lettuce for a bit.