<i>Salmonella enterica</i> Infections in the United States and Assessment of Coefficients of Variation: A Novel Approach to Identify Epidemiologic Characteristics of Individual Serotypes, 1996–2011

<div><p>Background</p><p>Despite control efforts, salmonellosis continues to cause an estimated 1.2 million infections in the United States (US) annually. We describe the incidence of salmonellosis in the US and introduce a novel approach to examine the epidemiologic similarities and differences of individual serotypes.</p><p>Methods</p><p>Cases of salmonellosis in humans reported to the laboratory-based National <i>Salmonella</i> Surveillance System during 1996–2011 from US states were included. Coefficients of variation were used to describe distribution of incidence rates of common <i>Salmonella</i> serotypes by geographic region, age group and sex of patient, and month of sample isolation.</p><p>Results</p><p>During 1996–2011, more than 600,000 S<i>almonella</i> isolates from humans were reported, with an average annual incidence of 13.1 cases/100,000 persons. The annual reported rate of <i>Salmonella</i> infections did not decrease during the study period. The top five most commonly reported serotypes, Typhimurium, Enteritidis, Newport, Heidelberg, and Javiana, accounted for 62% of fully serotyped isolates. Coefficients of variation showed the most geographically concentrated serotypes were often clustered in Gulf Coast states and were also more frequently found to be increasing in incidence. Serotypes clustered in particular months, age groups, and sex were also identified and described.</p><p>Conclusions</p><p>Although overall incidence rates of <i>Salmonella</i> did not change over time, trends and epidemiological factors differed remarkably by serotype. A better understanding of <i>Salmonella</i>, facilitated by this comprehensive description of overall trends and unique characteristics of individual serotypes, will assist in responding to this disease and in planning and implementing prevention activities.</p>