Map Shows Hepatitis A Cases As Outbreak Linked to Frozen Clams - Newsweek

A multistate outbreak of hepatitis A has been linked to imported frozen clams, according to the Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA).

Of the 37 known cases, 30 people have been hospitalized, though no deaths have been reported. The CDC has cautioned that the true number of illnesses may be higher because some infected people recover without seeking medical care or being tested.

Newsweek reached out to the CDC via email for comment.

The CDC has reported that illness onset dates range from July 30, 2025, to June 23, 2026, and among the 37 patients, ages ranged from 6-40 years old.

States affected include Massachusetts and Minnesota, both with three reported outbreak cases, Pennsylvania with four reported cases and New York with 27 outbreak-related cases of hepatitis A.

As part of a CDC and FDA investigation, state and local public health officials interviewed people about the foods they ate in the 15-50 days before they got sick.

Of those interviewed, 77 percent reported eating ceviche (raw fish or shellfish marinated in citrus juice), 76 percent reported eating raw or undercooked shellfish and 47 percent reported eating raw or undercooked black clams or conchas negras.

The percentages were deemed significantly higher than average when compared to the CDC FoodNet Population Survey, which helps estimate how often people eat various foods, suggesting a link between the outbreak and raw or undercooked clams.

La Serranita-brand concha negra, or black shell, fresh frozen clams from Ecuador were recalled earlier in the year, with an FDA announcement released in April outlining the products had been recalled in New York and New Jersey.

Then the FDA linked the product to restaurants and retailers in Connecticut, Massachusetts, New Jersey, New York, Ohio, and Pennsylvania.

Newsweek reached out to La Serranita via email for comment.

Illness as a result of frozen shellfish is unusual but not unprecedented. In 2016, an outbreak of hepatitis A in Hawaii was linked to imported raw scallops which caused 292 cases, 74 hospitalizations and two deaths. A 1991 paper published by the CDC recounted a similar investigation undertaken in 1988 when a multistate outbreak of hepatitis A was linked to raw oysters from Panama City, Florida.

Despite a recall some months ago, a CDC and FDA investigation into the outbreak is still ongoing. Anyone who ate the recalled frozen clams within the past 14 days and is not vaccinated against hepatitis A should speak with a healthcare provider or local health department about possible preventive treatment.

This is not the first time this year that frozen seafood has prompted action from the FDA. In March, the FDA announced a multistate recall for oysters and Manila clams harvested in Washington state after a cluster of norovirus‑like illnesses was linked to raw shellfish consumption.

In the U.S., imported seafood is monitored through the FDA’s seafood safety program, which includes inspections, HACCP (Hazard Analysis Critical Control Point) requirements and import screening. Imported seafood is legally required to meet the same safety standards as domestic products.

Experts note that hepatitis A can be particularly challenging to detect in shellfish. In a 2009 paper, researchers from the department of microbiology and Institute of Nutrition and Food Safety at the University of Barcelona explained that because contamination may occur at very low levels and not be present in every sample taken from an affected batch, routine testing does not always identify contaminated products before illnesses occur.

Not everyone infected with hepatitis A will develop symptoms, and when symptoms do occur they typically appear two to seven weeks after exposure to the virus.

According to the CDC, common symptoms include fever, fatigue, loss of appetite, nausea, vomiting, stomach pain, diarrhea, dark urine, clay-colored stools, joint pain, and jaundice, a yellowing of the skin or eyes.

While most people will recover within a few weeks, in rare cases hepatitis A can cause liver failure, particularly among older adults and people with existing conditions.

Update 9/23/26, 5:35 a.m. ET: This story was updated to outline when the clams were recalled.