Importation

Perhaps no feature so dramatically illustrates the changes in food-borne illness etiology as importation. All commodities from meat, poultry, dairy, fish, grains, produce, and processed foods have been affected to varying degrees. Greater ethnic diversity in the industrialized nations results from immigration from developing countries, with each immigrant group having its unique cultural food preferences. Nearly 50 million persons now travel yearly from the industrialized world to Asia, Africa, and Latin America, where they experience varied cuisines and novel foods. Both these trends have increased demand in the industrialized nations for exotic food products obtainable either more cheaply or only through importation.

Fresh fruits and produce are now regularly imported into the industrialized nations, following the harvest season through the year around the globe. An entire generation now expects otherwise seasonal produce items to be routinely available year round. Fruit and vegetable crops in the developing world may be grown and harvested under conditions quite different from those for produce grown in the United States. Consumption of imported contaminated foods has caused illness with common pathogens such as salmonella, or exotic pathogens such as Cyclospora (Herwaldt et al., 1997) or Vibrio cholerae (Taylor et al., 1993). Even insubstantial exposures can result in illness when the infectious dose of a pathogen is low and there is little pre-existing immunity in the population. In the outbreaks of cyclo-sporiasis associated with imported raspberries, the berries often were only used as a garnish yet attack rates were often greater than 80 percent (Herwaldt et al., 1997).

Currently there are no regulatory standards for microbiological criteria for fresh produce in the United States. Many of these, such as salad items and fruits, are consumed raw, offering immediate opportunity for ingestion of pathogenic organisms distinctly uncommon in the developed world. It is no longer necessary to travel abroad to acquire enterotoxigenic E. coli, the most common cause of traveler's diarrhea (Naimi et al., 2003; Beatty et al., 2006; Daniels, 2006). "Don't eat the salad" is a key piece of pre-travel advice for travelers to the developing world, yet salad consumed domestically represents some risk as well. In the US, the proportion of outbreaks associated with fresh produce increased ten-fold between 1977 and 1997 (see Figure 8.1), and the implicated vehicles (lettuce, juice, melon, sprouts, and berries) all would be considered "healthy" foods (Sivapalasingam, 2004).

Preparation of fresh produce to be served raw requires extensive handling, such as peeling, slicing, chopping, or shredding. These manual operations in

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□ Number of outbreaks □ Number of individuals

1970s

1980s Year

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Figure 8.1 Outbreaks of food-borne illness associated with fresh produce in the United States, 1973-1997. Reproduced with permission of the Institute of Medicine (2003a).

1970s

1980s Year

1990s

Figure 8.1 Outbreaks of food-borne illness associated with fresh produce in the United States, 1973-1997. Reproduced with permission of the Institute of Medicine (2003a).

commercial processing create opportunities for contamination by infected food handlers in processing facilities. These workers are often poorly educated, have low wages and no benefits such as sick time or health insurance, and worker turnover may approach 50 percent per year. This confluence of factors makes it difficult to provide and reinforce training in sanitation and hygienic food preparation practices, and workers have only economic disincentives to stay out of work when ill. Mass production, chilled storage, and widespread distribution have repeatedly amplified food-handler associated outbreaks involving fresh produce.

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