Number of Outbreaks of Disease Associated with Imported Food Increasing


CDC researchers found that not only is the proportion of US food that is imported is increasing, but the number of food-borne disease outbreaks associated with imported foods is also increasing.

The Centers for Disease Control and Prevention (CDC) report that about 1 in 6 Americans, (48 million individuals), fall ill from food-borne illnesses each year, which makes improving food safety practices all the more important.

Food importation has increased over the past 20 years and as such, it is estimated that 19% of the food Americans consumed is imported. By taking a closer look at disease outbreaks associated with imported food, CDC researchers have identified the types of food most commonly involved in food-borne illness outbreaks as well as the countries they came from. Taking into consideration these findings, the researchers stress that “new outbreak investigation tools and federal regulatory authority are key to maintaining food safety.”

A food-borne outbreak occurs if two or more individuals fall ill with a “similar illness resulting from ingestion of a common food.” The CDC receives reports pertaining to food-borne outbreaks through the Foodborne Disease Outbreak Surveillance System, a system that local, state, and territorial health departments use to input data. For each outbreak, data regarding where and when the outbreak occurred, the number of individuals who fell ill or presented with related symptoms, the food associated with the outbreak, the pathogen responsible for the outbreak, and “where the implicated food originated” are collected.

For their study, CDC researchers took a closer look at disease outbreaks associated with imported food that occurred since the surveillance system had been put into place (in 1973) up until 2014 (the most recent year of available data).

The researchers categorized the foods associated with outbreaks according to schema that had been created by the Interagency Food Safety Analytics Collaboration. Furthermore, the researchers used the United Nations Statistics Division classification to group countries. With this information, the researchers conducted “a descriptive analysis” detailing the number of food-borne outbreaks that occurred during that defined time period, “by food category, and by region of origin.”

Between 1996 and 2014, a total of 195 outbreaks “implicated an imported food, resulting in 10,685 illnesses, 1,017 hospitalizations, and 19 deaths.” In addition, outbreaks associated with imported food accounted for an “increasing proportion of all food-borne disease outbreaks,” with 1% reported between 1996 and 2000, and rising to 5% between 2009 and 2014. The average of imported food-associated outbreaks also increased from 3 per year for the time period of 1996 to 2000 to about 18 per year from 2009 to 2014.

The most common agents associated with these outbreaks were Scombroid toxin and Salmonella; with Salmonella and Cyclospora accounting for most associated illnesses. In addition, the researchers also found that in more than half (55%) of the outbreaks, “aquatic animals” were the culprits; they also accounted for 11% of outbreak-associated illnesses.

Although produce was accountable for 33% of the outbreaks, it was also responsible for a whopping 84% of outbreak-associated illnesses. The researchers noted that “outbreaks attributed to produce had a median of 40 illnesses compared with a median of 3 in outbreaks attributed to aquatic animals.” The majority of the Salmonella outbreaks were reported to have been associated with produce (77%) such as fruits (14 outbreaks), seeded vegetables (10), sprouts (6), nuts and seeds (5), spices (4), as well as herbs (1), according to the CDC.

For 177 outbreaks (91%), data were available pertaining to the implicated food’s region of origin. The most common regions of origin were Latin America and the Caribbean, with Asia following close behind. In total, 31 countries were implicated, with Mexico “most frequently implicated” (42 outbreaks). Indonesia and Canada were also noted to have 17 and 11 outbreaks, respectively.

With the exception of Europe, fish and shellfish were noted to have originated from all regions, “but [fish and shellfish associated with outbreaks] were most commonly imported from Asia (65% of outbreaks associated with fish or shellfish).” Similarly, produce originated from all regions as well, but “was most commonly imported from Latin America and the Caribbean (64% of outbreaks associated with produce).” Furthermore, “all but one outbreak associated with dairy products involved products from Latin America and the Caribbean.”

According to the researchers, outbreaks were reported in 31 states, with California taking the lead in the number of imported food-associated outbreaks (30 outbreaks), followed by Florida (25) and New York (16). Furthermore, a total of 43 outbreaks (22%) were multistate outbreaks.

The researchers came to the conclusion that despite the fact that the number of imported food-associated outbreaks is not very large, it has increased over time, and imported fish and produce were the most common food types associated with these outbreaks. Latin America and the Caribbean are major sources of fruits and vegetables for the United States due to their proximity; however, produce coming from these regions were involved in many of the noted outbreaks. Mexico was most frequently implicated as a region of origin for many of the imported foods associated with outbreaks, and it “is [also] the source of about one quarter of the total value of fruit and nut imports and 45%-50% of vegetable imports.” The fact that one quarter of the outbreaks were multistate outbreaks indicates how imported foods are extensively distributed throughout the country.

This increase in imported food-related outbreaks “underscores the need to strengthen regional and global networks for outbreak detection and information sharing,” according to the authors. “Our findings reflect current patterns in food imports and provide information to help guide future outbreak investigations. Prevention focused on the most common imported foods causing outbreaks, produce and seafood, could help prevent outbreaks. Efforts to improve the safety of the food supply can include strengthening reporting by gathering better data on the origin of implicated food items, including whether imported and from what country."

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