A salmonella outbreak linked to oysters has sickened at least seven people in New York and dozens more nationwide.

The U.S. Centers for Disease Control and Prevention is trying to determine if there is a common source for the oysters.

The CDC reports that people who fell ill ate raw oysters. 

The outbreak stretches across the U.S. with cases reported in California, Texas, Florida and Colorado and at least 18 others states.

Every state on the Eastern Seaboard but New Hampshire had seen at least one case.

The CDC says at least 64 people have been sickened but the number is likely higher “because many people recover without medical care and are not tested for salmonella.”

So far, the highest number of illnesses, 10, were reported in Pennsylvania with New York’s seven cases good for the second highest.

Salmonella is a common food-borne illness that can cause intestinal issues, including diarrhea and cramps. It can also cause fever and diarrhea, which can lead to dehydration. The CDC estimates that it annually causes about 1.35 million infections in the U.S.