Hawaii’s hepatitis A outbreak, which has sickened 241 people so far, is the worst in the country since 2003 and a sharp reversal from the downward trajectory of the disease in recent decades.

The culprit this time is tainted bay scallops, imported frozen from the Philippines and served raw as sushi. Meanwhile, frozen strawberries from Egypt are being blamed for a hepatitis A outbreak tied to smoothies, with 81 victims as of Friday, mostly in Virginia.

A few years ago pomegranate seeds from Turkey felled 165 people with hepatitis A, including eight in Hawaii. Green onions from Mexico triggered the biggest outbreak, claiming 601 victims in Pennsylvania and 324 in other states in 2003, according to the Centers for Disease Control and Prevention.

Widespread vaccination has helped push down hepatitis A rates in the United States by more than 90 percent since 2000. But the latest outbreaks are highlighting the possibility of contamination from far afield in the global food chain.

“Nowadays many modern or First World countries don’t have the agricultural resources or lands or ocean or persons to sustain ourselves, to feed ourselves,” said Dr. Sarah Park, state epidemiologist. “And so we rely heavily on importing from other regions of the world.

“We have to think about the fact that foods are coming from other places where the standards are not quite the same.”

Hepatitis A, a contagious liver disease, spreads when people ingest food or water contaminated with traces of human feces, or through close personal contact. International travel is a major risk factor for Americans in contracting the virus, and vaccines are recommended before visiting developing countries.

Investigators are trying to trace how the Philippine bay scallops implicated in the current outbreak were contaminated. It’s possible there was a sewage spill in the bay where the scallops were harvested, or they were processed in tainted water or an ill worker passed on the infection.

Asked what the U.S. Food and Drug Administration considers the most likely point of contamination, an agency spokeswoman declined to say.

“This is an ongoing investigation and we will refrain from speculation,” Lauren Sucher, FDA press officer, said Friday. “The FDA is currently reviewing information about the supply chain of these scallops and will conduct further investigation as necessary.”

The scallops were produced, frozen and packed by De Oro Resources Inc. in Suba Basbas, Philippines, on Nov. 23 and 24, and were imported by Sea Port Products Corp. of Kirkland, Wash. On its website Sea Port says the Philippine bay scallops are caught by divers or dredged, then shucked by hand on shore, usually by the fishermen.

Sea Port immediately recalled three lots of the frozen scallops — 24,000 pounds — after two samples taken by the FDA of one lot tested positive for hepatitis A. FDA tests of the other lots were negative, said Amy Philpott, spokeswoman for Sea Port Products.

Sea Port stopped importing scallops from De Oro, and the Philippine company has not been shipping because of the ongoing investigations, she said.

A family-owned company, Sea Port is working with health officials and the supplier to examine every step in the supply chain, according to owner Bill Dresser.

“To our knowledge, this is the first time ever that scallops from any origin have been implicated in a hepatitis A outbreak, and we are working closely with regulators and our supply chain partners to try to determine how this might have happened,” Dresser said.

”We have been doing business in Hawaii for more than 30 years, and I consider Hawaii a second home,” he added. “I am deeply troubled at the thought that anyone may have become ill from eating product that we shipped.”

The FDA is responsible for ensuring the safety of the nation’s food supply, working with state and local authorities. According to the agency’s 2013 annual report, FDA physically examined 1.9 percent of food import lines, focusing on products that posed the greatest risk based on electronic screening of all imports.

In 2012 an outbreak of norovirus — not the hepatitis A virus — prompted FDA to block shipments of oysters and other shellfish from South Korea for fear waters there were polluted with human waste. The ban was lifted the following year.

“A ban from U.S. commerce is actually a removal from the Interstate Certified Shellfish Shippers List,” the FDA’s Sucher said. “From time to time, areas within the U.S. or overseas may be removed from the list due to sanitation issues in the shellfish-growing waters.”

Asked under what circumstances FDA would ban imports from De Oro, she said, “The FDA is continuing to investigate, and will act if we uncover evidence that other lots or products are potentially contaminated.”

Foodborne illness outbreaks in Hawaii tend to be limited in time and scope, Park said. But this one took off because the scallops reached a lot of people quickly through Genki Sushi’s 10 restaurants scattered across Oahu.

“In a way it was just poor luck for us,” she said. “It could have been a contaminated food product that had a very small market or was used only by a few families or few parties. Unfortunately, it was something that was sold to a very popular, common restaurant chain that has affordable pricing, so that makes it doubly popular.”

On the plus side, vigilance by the state Health Department, local restaurants and residents has helped in keeping the outbreak from escalating much beyond those who ate scallop sushi. So far, just a handful of secondary cases have surfaced among people who caught it within their household from a primary case, she said.

Nora Spencer-Loveall, spokeswoman for the Centers for Disease Control and Prevention, praised the state’s response.

“The Hawaii Health Department has led from the beginning,” she said. “I think they’ve done a great job. They’ve identified a source, they’ve stopped transmission.”

Over the last decade Hawaii averaged just 10 cases of hepatitis A annually. Nationally the number of hepatitis A cases fell from 13,397 in 2000 to to 1,239 in 2014, the last year for which federal data are available. The national rate of infection, 0.4 cases per 100,000 people, matched the rate in Hawaii in 2014.

The Health Department encourages Hawaii residents to consult with their doctors about getting a hepatitis A vaccine, which provides long-lasting protection. Hepatitis A is a hardy virus that can remain infectious on environmental surfaces for a month or more. It withstands freezing, but is destroyed when food is cooked to 185 degrees for one minute.

“It is the only foodborne disease that is vaccine-preventable, so it’s a simple protection,” Park said.