Early detection of influenza outbreaks using the DC Department of Health's syndromic surveillance system.

BACKGROUND: Since 2001, the District of Columbia Department of Health has been using an emergency room syndromic surveillance system to identify possible disease outbreaks. Data are received from a number of local hospital emergency rooms and analyzed daily using a variety of statistical detection algorithms. The aims of this paper are to characterize the performance of these statistical detection algorithms in rigorous yet practical terms in order to identify the optimal parameters for each and to compare the ability of two syndrome definition criteria and data from a children's hospital versus vs. other hospitals to determine the onset of seasonal influenza. METHODS: We first used a fine-tuning approach to improve the sensitivity of each algorithm to detecting simulated outbreaks and to identifying previously known outbreaks. Subsequently, using the fine-tuned algorithms, we examined (i) the ability of unspecified infection and respiratory syndrome categories to detect the start of the flu season and (ii) how well data from Children's National Medical Center (CNMC) did versus all the other hospitals when using unspecified infection, respiratory, and both categories together. RESULTS: Simulation studies using the data showed that over a range of situations, the multivariate CUSUM algorithm performed more effectively than the other algorithms tested. In addition, the parameters that yielded optimal performance varied for each algorithm, especially with the number of cases in the data stream. In terms of detecting the onset of seasonal influenza, only "unspecified infection," especially the counts from CNMC, clearly delineated influenza outbreaks out of the eight available syndromic classifications. In three of five years, CNMC consistently flags earlier (from 2 days up to 2 weeks earlier) than a multivariate analysis of all other DC hospitals. CONCLUSIONS: When practitioners apply statistical detection algorithms to their own data, fine tuning of parameters is necessary to improve overall sensitivity. With fined tuned algorithms, our results suggest that emergency room based syndromic surveillance focusing on unspecified infection cases in children is an effective way to determine the beginning of the influenza outbreak and could serve as a trigger for more intensive surveillance efforts and initiate infection control measures in the community.

Elevated lead in drinking water in Washington, DC, 2003-2004: the public health response.

BACKGROUND: In 2003, residents of the District of Columbia (DC) experienced an abrupt rise in lead levels in drinking water, which followed a change in water-disinfection treatment in 2001 and which was attributed to consequent changes in water chemistry and corrosivity. OBJECTIVES: To evaluate the public health implications of the exceedance, the DC Department of Health expanded the scope of its monitoring programs for blood lead levels in children. METHODS: From 3 February 2004 to 31 July 2004, 6,834 DC residents were screened to determine their blood lead levels. RESULTS: Children from 6 months to 6 years of age constituted 2,342 of those tested; 65 had blood lead levels > 10 microg/dL (the "level of concern" defined by the Centers for Disease Control and Prevention), the highest with a level of 68 microg/dL. Investigation of their homes identified environmental sources of lead exposure other than tap water as the source, when the source was identified. Most of the children with elevated blood lead levels (n = 46; 70.8%) lived in homes without lead drinking-water service lines, which is the principal source of lead in drinking water in older cities. Although residents of houses with lead service lines had higher blood lead levels on average than those in houses that did not, this relationship is confounded. Older houses that retain lead service lines usually have not been rehabilitated and are more likely to be associated with other sources of exposure, particularly lead paint. None of 96 pregnant women tested showed blood lead levels > 10 microg/dL, but two nursing mothers had blood lead levels > 10 microg/dL. Among two data sets of 107 and 71 children for whom paired blood and water lead levels could be obtained, there was no correlation (r(2) = -0.03142 for the 107). CONCLUSIONS: The expanded screening program developed in response to increased lead levels in water uncovered the true dimensions of a continuing problem with sources of lead in homes, specifically lead paint. This study cannot be used to correlate lead in drinking water with blood lead levels directly because it is based on an ecologic rather than individualized exposure assessment; the protocol for measuring lead was based on regulatory requirements rather than estimating individual intake; numerous interventions were introduced to mitigate the effect; exposure from drinking water is confounded with other sources of lead in older houses; and the period of potential exposure was limited and variable.

Clinical spectrum and histopathologic features of chronic hepatitis C infection in children.

OBJECTIVE: To define the natural history and outcomes of children infected with hepatitis C virus (HCV) at birth or in early childhood. STUDY DESIGN: This retrospective, prospective study identified 60 HCV-infected children through a transfusion look-back program (group 1) and by referrals (group 2). Perinatal/transfusion history, clinical course, and laboratory studies were correlated with findings from 42 liver biopsy specimens. RESULTS: Mean age at infection was 7.1 months, and duration of infection 13.4 years. The sources of infection were blood transfusion (68%), perinatal transmission (13%), and both (7%). Most patients were asymptomatic; three referral patients had advanced liver disease at presentation. Mean alanine aminotransferase level was normal in 25%, 1 to 3 times normal in 62%, and greater than 3 times normal in 13%. Liver biopsy specimens showed minimal to mild inflammation in 71%, absent or minimal fibrosis in 88%, and bridging fibrosis in 12%. Age at infection and serum gamma-glutamyltranspeptidase correlated with fibrosis; serum alanine aminotransferase correlated with inflammation unless complicated by comorbidity. Repeat biopsies within 1 to 4 years in four patients showed no significant progression in three and cirrhosis in one. Two patients died after liver transplantation. CONCLUSIONS: Children with chronic HCV infection are generally asymptomatic. By 13 years after infection, 12% of patients had significant fibrosis. Patients enrolled by referral had more severe liver disease than those identified through the look-back program, demonstrating the importance of selection bias in assessing the long-term outcome of HCV infection.