Figuring out that pomegranate seeds from Turkey are likely what is responsible for infecting at least 132 people with Hepatitis A was unusually difficult, according to investigators at the U.S. Food and Drug Administration. The ongoing investigation into the outbreak, which spans 8 states, is “very, very complicated,” said Carla Tuite, the lead on the response team handling the outbreak at FDA. Tuite is part of the agency’s Coordinated Outbreak Response and Evaluation (CORE) Network, a multidisciplinary team that works closely with states and the Centers for Disease Control and Prevention to solve foodborne illness outbreaks. “It’s a challenging outbreak due to the type of contaminant,” said Tuite, during a CORE interview with Food Safety News on Tuesday. “It’s unusual to get a virus in a product. When you’re talking about traceback and making sure you have all the right epidemiological information, it can be challenging.” “I think of all the investigations we’ve been on, this is one of the ones that’s been the most challenging we’ve faced,” she added. While public health officials had linked the growing outbreak to Townsend Farms Organic Antioxident Blend, a frozen berry mix, more than a month ago, they had not definitively identified which of the five types of berries in the blend was the culprit. Over the weekend, FDA announced they had traced the problem back to a common lot of pomegranate seeds from Turkey, sold by Goknur Foodstuffs Import Export Trading. The agency said it would detain any further pomegranate seeds from the company at ports of entry. When asked how much product was impacted by the import action, Tuite noted that the situation is still developing, but said it was “a large lot, a large amount of pomegranate seeds that come into the country.” Last week, Scenic Fruit recalled 60,000 packages of pomegranate seeds, which were also imported from Turkey, out of concern they might have been linked to the outbreak. Now, FDA investigators are in overdrive trying to figure out where else the imported pomegranate seeds might have been sold and whether there need to be more recalls. According to Kathleen Gensheimer, the chief medical officer and director of CORE, one of the most challenging factors in this outbreak is the lengthy incubation period for the hepatitis A virus. Once exposed, it can take anywhere from 15 to 50 days to get sick, and people usually do not remember what they ate a month ago, or even a few days ago. Making the situation even more complicated, the implicated berry blend contains five types of berries, which were sourced from different farms in various countries. On the Townsend Farms package it says the berries were from Turkey, Chile, Argentina, and the United States. “No epidemiologic interviews on the part of the patients really could have distinguished whether it was the strawberries, the raspberries, the cherries, the blueberries, or the pomegranates from this frozen blend,” explained Gensheimer. She said FDA honed in on the pomegranate seeds through “very, very tedious, time consuming, and very careful analysis” of all the records provided by Townsend Farms. Through this extensive traceback effort, investigators were able to identify a common lot of that was used in products that had been linked to cases of hepatitis A. Luckily, the pomegranate seeds were the only commonality. “What I compare it to is a 25,000 piece jigsaw puzzle,” said Gensheimer. “When you try to put all these pieces together and have them make sense, it is truly, truly tedious.” The other complicating factor is that it can be tricky to find hepatitis A in food products. “It’s not like Salmonella or an E.coli organism,” explained Gensheimer. “A virus is just different than a bacteria it’s not something you can grow out on a special media.” She said special methods had to be developed by FDA in the early stages of the outbreak to help investigators look for possible contamination. “We’ve yet to identify any positive product,” she said. “I’m not really sure that that represents a lack of contaminated product or a lack of a test that is quite there yet as far as being able to look for evidence of the hepatitis A virus.” While the next steps are not yet clear, FDA is coordinating with Turkey on the matter. “There is strong interest on the part of Turkey – they obviously have some political issues going on at the moment – but in the initial conversations FDA has had with the Turkish government, it’s clear they’re very concerned about this,” Gensheimer said of the current outbreak, noting that the Turkish government said it had sent someone to look into the plant at the center of the issue. FDA spokesman Doug Karas said FDA is communicating with Turkey’s Ministry of Food, Agriculture and Livestock.