The Centers for Disease Control and Prevention has confirmed 37 hepatitis A illnesses over the past year across four states that are possibly connected to frozen clams.
The states were Massachusetts, Minnesota, New York, and Pennsylvania, the CDC said in a Sept. 18 release. The illness onset dates were from June 30, 2025, to June 23, 2026, the CDC said. No deaths have been reported, but 30 people were hospitalized.
Three cases were reported in Massachusetts, three in Minnesota, 27 in New York, and four in Pennsylvania, according to the CDC. The age range of those who were ill was from 6 to 40 years old.
After public health officials interviewed the ill people about the foods they had consumed in the 15 to 50 days before they got sick, 76 percent said they ate raw or undercooked shellfish; 47 percent reported eating raw or undercooked black clams; and 77 percent reported eating ceviche, or raw fish or shellfish marinated in citrus juice.
These percentages were “significantly higher” than the percentage of respondents who reported eating ceviche or raw or undercooked seafood or shellfish, including clams, in a broader survey that allows officials to estimate how often people eat various foods connected to diarrheal illnesses, the CDC said.
Those people may have become ill from eating raw or undercooked clams, the CDC stated.
The federal health agency warned that the actual number of people who became ill from hepatitis A is probably higher than what has been reported to the CDC. It stated that more recent illnesses may not have yet been reported and that the outbreak may have spread to other states.
“During the outbreak, epidemiologic data showed that imported frozen clams may have been contaminated with hepatitis A virus and made people sick in this outbreak,” the CDC said. “Traceback investigations are ongoing to identify the source or sources of frozen clams that were consumed raw or undercooked by people who are ill.”
The CDC listed one product in its outbreak alert, saying that La Serranita-brand concha negra, or black shell, products have been recalled by dealers in New Jersey and New York due to hepatitis A.
The shell meat product was distributed in Connecticut, Massachusetts, New Jersey, New York, Ohio, and Pennsylvania, the Food and Drug Administration said in a May alert.
Hepatitis A is a contagious liver infection caused by the hepatitis A virus, which can spread via close contact with an infected individual, food, or water, the World Health Organization says on its website.
Most people who contract the viral infection recover fully and have lifelong immunity, according to the U.N. health agency. Unlike hepatitis B and hepatitis C, it does not cause chronic, lifelong liver disease.
A small number of people, however, can die from fulminant hepatitis, which is a life-threatening health emergency in which the liver fails quickly—sometimes within days, the Mayo Clinic’s website says.
In 2023, at least 35,569 people died from hepatitis A around the world, the World Health Organization said, and it stated that the virus “occurs sporadically and in epidemics worldwide with a tendency for cyclic recurrences.”