and enhanced outbreak investigations, and their probable link to recent reductions in cases of several major foodborne diseases.

Despite these improvements, the processes of outbreak detection and investigation remain highly challenging, as illustrated in the case studies that make up the remainder of this chapter. The first two papers, by Barbara Herwaldt of the CDC and Roberta Hammond and Dean Bodager of the Florida Department of Health, describe their experiences investigating a relatively new foodborne threat: the coccidian parasite Cyclospora cayetanensis. Little was known about the organism when, in the mid-1990s, large, multistate outbreaks of gastroenteritis were recognized. Herwaldt and public health colleagues eventually traced these outbreaks to raspberries from Guatemala, where Cyclospora infection is endemic. Several other types of fresh produce have also been identified as vehicles for cyclosporiasis outbreaks. Herwaldt analyzes the challenges presented by foodborne outbreaks (in general, as well as the specific difficulties associated with C. cayetanensis) and draws important lessons for the future of public health.

In the subsequent paper, Hammond and Bodager describe the complexities of a recent C. cayetanensis investigation. Triggered by an early 2005 report from a private lab of an unusually large number of infections, the investigation ultimately involved county health departments throughout Florida, three different state agencies that regulate food in Florida, and two federal agencies: the CDC and the Food and Drug Administration (FDA). The investigators determined that imported basil provided the vehicle for the parasite; like raspberries, basil is a “stealth” ingredient that many people do not recognize or (because such foods are often served as garnishes) easily forget. Such accounts illustrate the importance of examining seemingly unrelated cases of apparent foodborne illnesses as indicators of outbreaks and pursuing them to their sources through timely and thorough investigation.

The pathogen discussed in the chapter’s final contribution, the hepatitis A virus (HAV), is far better characterized than Cyclospora, yet its investigators are faced with a similar array of challenges. This paper, by workshop speaker Beth Bell and Anthony Fiore of the CDC, describes a series of hepatitis A outbreaks in late 2003 that included the largest such outbreak reported in the United States. It involved over 600 patrons of a single Pennsylvania restaurant, and ultimately led the FDA to ban imports from the Mexican farms that grew the tainted green onions that caused the outbreak. Investigators were aided by molecular methods for HAV detection (comparable methods do not exist for Cyclospora), but Bell and Fiore note several characteristics of routine hepatitis A surveillance and of the infection itself that continue to hinder its detection and control. The authors conclude that foodborne HAV infection (and those of other enteric pathogens) may be best prevented on the farm by reducing the contamination of produce with fecal material.

Taken as a whole, the papers in this chapter demonstrate both the crucial importance and the daunting difficulty of conducting foodborne outbreak investi-



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