Outbreaks of Salmonella enterica Linked to Animal Contact: Demographic and Outbreak Characteristics and Comparison to Food Outbreaks — United States, 2009–2014

Introduction: Each year in the United States, Salmonella enterica infections cause an estimated 1.2 million illnesses that result in 19,000 hospitalizations and 390 deaths. Illnesses occur sporadically throughout the year, but might also occur as part of an outbreak. Outbreaks are most commonly linked to a food source, but contact with live animals can also result in human outbreaks of illness. Methods: Outbreaks of Salmonella reported to the Centers for Disease Control and Prevention through National Outbreak Reporting System (NORS) from 2009–2014 with a primary mode of transmission listed as animal contact or food were analyzed to characterize the demographics of zoonotic outbreaks and examine how they differ from foodborne outbreaks. Missing data for age or sex categories were recoded as age or sex unknown. Chi-square tests were conducted to compare proportions of categorical variables. Logistic regression was used to calculate odds ratios for age, sex, health outcomes and multistate exposure. Wilcoxon rank-sum tests were used to compare medians for outbreak size and duration. Analyses were conducted using SAS 9.3. Results: During 2009–2014, a total of 484 outbreaks were reported through NORS; of these, 99 (20.5%) resulted from Salmonella transmission through animal contact and 385 (79.5%) resulted from foodborne transmission. These outbreaks resulted in 3,604 (19.8%) and 13,568 (80.2%) illnesses, respectively. A higher proportion of outbreak-associated illnesses among children aged(15.2% vs. 1.4%, p Conclusions: Outbreaks of Salmonella resulting from animal contact frequently have characteristics that are distinct from food outbreaks. Findings are consistent with reports in the literature where young children are disproportionately affected by animal contact outbreaks. Animal contact outbreaks might have a higher proportion of hospitalizations, emergency room visits, and healthcare provider visits. Animal contact outbreaks might also be longer in duration and are more likely to be multistate. Future investigations of multistate Salmonella outbreaks that are consistent with these differences should collect epidemiologic information regarding animal exposures to determine if contact with animals resulted in the transmission of the outbreak