Strategies for Surveillance of Pediatric Hemolytic Uremic Syndrome: Foodborne Diseases Active Surveillance Network (FoodNet), 2000–2007

Hemolytic uremic syndrome (HUS) is a severe sequela of Shiga toxin–producing Escherichia coli (STEC) O157 infection characterized by hemolytic anemia, thrombocytopenia, and kidney failure. More than 90% of HUS cases follow a diarrheal illness and most are attributable to STEC O157 infection [1]. HUS is the most common cause of acute renal failure among US children <5 years of age [2, 3]; of the estimated 93 000 domestically acquired STEC O157 infections in the United States each year [4], approximately 6% will develop HUS [2]. The mortality rate is approximately 5% [2]. HUS may result in major long-term complications, including chronic renal failure, neurologic dysfunction, and hypertension [5]. Providing appropriate supportive care in a timely manner improves outcomes [6]. Surveillance for HUS provides a way to monitor trends in STEC O157 infections, can help to assess which strains of STEC are associated with severe outcomes, and can evaluate whether improvements in medical care are leading to less frequent development of HUS in children infected with STEC. For example, trends in STEC O157 infections can be influenced by changes in diagnostic practices. By providing a stable marker of STEC incidence, HUS surveillance can be used to determine the effectiveness of preventive measures. HUS surveillance is complicated by the lack of a single diagnostic test and the need for multiple data elements to validate each reported case. The significance of HUS as a public health issue was reflected in the Healthy People 2010 goal to reduce the incidence of postdiarrheal HUS among children <5 years of age by 50% (to 0.9 cases per 100 000) [7]. The Foodborne Diseases Active Surveillance Network (FoodNet) conducts active surveillance for HUS in children <18 years using 2 complementary case ascertainment methods. We compare the finding of these 2 methods of case ascertainment and the impact of different case definitions on surveillance data from 2000 to 2007.