In recent years, fourteen percent of the U.S. food supply has been imported from other countries, including many fresh and perishable foods. Although most outbreaks of illness and individual cases are related to foods from the United States, large and unusual outbreaks have been traced to imported foods that were likely contaminated in the country of origin. Investigation of these outbreaks requires collaboration across several disciplines as well as across international borders. Successful investigation can not only control the original problem, but can also inform public authorities in both countries about the need for strategies to prevent similar outbreaks from happening in the future. Production of perishable foods in the developing world brings particular challenges because of the deficiencies in basic sanitation and hygiene and other elements of public health that Americans take for granted. The public health infrastructure in such countries is critical to identifying and controlling foodborne and waterborne challenges before they affect exported foods, and strengthening such infrastructure is an important part of general development efforts. Strategies to improve the health of the workers and rural populations in those countries and to increase the capacity of public health and food safety systems are likely to have long-term benefits to health in those countries, as well as preventing infections in the countries to which they export.
TABLE OF CONTENTS I. HISTORICAL INTRODUCTION II. AN INCREASINGLY INTERNATIONAL FOOD SUPPLY III. THE ART AND PRACTICE OF THE FOODBORNE OUTBREAK INVESTIGATION IV. ILLUSTRATIVE OUTBREAKS A. Cyclospora and Central American Raspberries B. Dysentery and Mexican Parsley C. Jaundice and Green Onions D. E. coli O157 and Alfalfa Seeds from Down Under E. Queso Fresco and Listeriosis F. The Unintended Consequence of a Regulation: Mangoes and Salmonella Newport V. TRANSLATING INVESTIGATIONS INTO IMPROVED FOOD SAFETY VI. IMPROVING DISEASE PREVENTION IN GENERAL VII. MONITORING THE CHANGING RISKS I. HISTORICAL INTRODUCTION
Food safety is a major and current public health challenge in the United States. The burden of illness has been estimated to be 76 million illnesses and over five thousand deaths each year. (1) Most of the recently recognized food safety challenges, including those related to meat, poultry, produce, and raw shellfish, concern food produced in this country. (2) The Institute of Medicine has reviewed these general challenges and recommended approaches to making further improvements in food safety in the United States. (3) It is also true that imported foods have presented a challenge in the last decade. The issues surrounding these imported foods are the focus of this Article.
Americans enjoy a food supply that is more ample, more nutritious, and safer than our forebears did one hundred years ago, when the publication of Upton Sinclair's novel The Jungle ushered in the modern era of food safety. (4) In 1906, the establishment of the forerunners of the Food and Drug Administration (FDA) and the Food Safety and Inspection Service (FSIS) of the U.S. Department of Agriculture (USDA) brought federal regulatory attention to the food supply. (5) The evolution of our food safety system since then has been spurred by recurrent large outbreaks of illness, informed by research findings from food and agricultural scientists, and driven by the demands of the food marketplace. Pasteurization of milk, reliable high-pressure canning, and the eradication of tuberculosis and trichinosis from our food animals have dramatically improved the safety of our food and are now taken largely for granted. (6) The current system is based on the "farm-to-table" philosophy, in which all the participants in the sequence of production, processing, and final preparation of our food have recognized roles in making the final food safe. (7) In the last decade, the safety engineering method called hazard analysis-critical control point (HACCP) has been applied in several sectors of the food industry and has seen real success in the meat industry. (8)
At the same time, our food has also become safer because of important changes in the health of the U.S. public, particularly in cities where more and more of us live. In the nineteenth and early twentieth centuries, food and water that were directly contaminated with human sewage were major sources of disease, causing epidemics of cholera, typhoid, and dysentery. (9) The "sanitary revolution" which brought us safe drinking water and sewage treatment was arguably the greatest advance in public health in the twentieth century. (10) The development of a robust public health system has also been an important factor. The U.S. has expanded public health notifiable disease surveillance at local, state, and national levels; introduced increasingly sophisticated methods for detecting and investigating outbreaks; and used the results of those investigations to guide continuous improvements in the prevention of foodborne disease. (11)
Now, many serious foodborne and waterborne infections are part of the remote past. Typhoid fever and cholera have become extremely rare, and the cases that occur in the U.S. are typically the result of travel to the developing world, where those same infections remain common. (12) Nonetheless, Salmonella, E. coli O157, Campylobacter, Vibrio, and other pathogens with major reservoirs in American food animals continue to cause large numbers of illnesses despite the progress that has been made. (13) The recent large outbreaks of infections with E. coli O157:H7 and Salmonellae associated with domestic spinach, lettuce, tomatoes, and peanut butter highlight the immediate need for major improvements in food safety here in the United States. (14) Many of these foodborne infections that challenge us now are the result of the contamination of our food with animal manure in this country. (15) The next great challenge of food safety in the U.S. may be to bring about an agricultural "sanitary revolution" to clearly separate animal manure from food and water supplies, and to make water, feed, and fertilizer for the animals and plants safer.
AN INCREASINGLY INTERNATIONAL FOOD SUPPLY
U.S. consumers, in pursuit of fresh foods that are available year round, appreciate an increasing array of perishable foods imported from other countries. The produce aisles of U.S. grocery stores are full of items that are produced and packed in other parts of the world, including many developing nations. (16) In 2001, eleven percent by weight of the entire U.S. food supply was imported, including twenty-three percent of fresh and frozen fruit, seventeen percent of fresh and frozen vegetables, and eighty-three percent of fresh and frozen seafood. (17) This represents a significant increase over past import figures. In comparison, back in 1980, only five to six percent of American fresh and frozen produce was imported. (18) Mexico is the source of twenty-seven percent of fruit imports, and other Latin American countries provide an additional forty percent. (19) One longstanding concern raised by these imports is the potential introduction of the Mediterranean fruit fly that would be harmful to American orchards. (20) This concern is overcome by irradiation, fumigation, or other treatments used to kill fruit fly larvae in fruit imported from areas known to have that insect. (21) The importation of fresh meat has been historically far more restricted because of concerns about animal diseases--such as hoof-and-mouth disease in cattle, or African swine fever--that have been eradicated from this country but remain endemic in other countries. (22) Because these animal diseases might damage domestic animal production if they are imported along with the meat from other countries, the fresh and frozen meat imported by the U.S. has come largely from Canada and Australia--countries with well-established animal disease control programs--and more recently from Argentina, after that country successfully eradicated hoof-and-mouth disease. (23) A curious situation thus emerges that many foods eaten without further cooking, including many fresh fruits and vegetables, are now imported from the same countries to which travelers are particularly advised to avoid fresh uncooked produce. (24) It is perhaps unsurprising, then, that outbreaks of foodborne illness in this country have been related to imported foods that became contaminated before they reached the U.S.
THE ART AND PRACTICE OF THE FOODBORNE OUTBREAK INVESTIGATION
An outbreak of foodborne illnesses occurs when a group of people become ill with the same infection after eating the same food. (25) CDC collects reports of outbreaks of foodborne diseases investigated by state health departments and publishes the results of this surveillance periodically. (26) The data collected rarely indicate the country of origin of the implicated food, probably because this is often not determined in the investigation. (27) In addition, CDC assists state health departments directly in conducting some investigations, particularly when there are large, severe, or multi-jurisdictional outbreaks. (28) Each investigation provides an opportunity to learn about the nature and source of the contamination, particularly when a specific food is implicated and then traced back to its source. A detailed public health investigation can reveal how contamination might likely have occurred and how it might be prevented. These investigations often have two goals: to control the immediate hazard and to reconstruct how it happened, so that similar outbreaks can be prevented in the future.
Outbreak investigations are usually labor-intensive epidemiological efforts to implicate the food that was likely the vehicle of transmission. Once a food is implicated, tracing its origin depends on the review of sales records and the cooperation of the...