Date of Award

January 2023

Document Type


Degree Name

Master of Public Health (MPH)


School of Public Health

First Advisor

James Hadler


Background: During 2020, Salmonella incidence decreased by 22% in the United States.1 At the same time, many common activities were reduced or restricted, including travel and eating food prepared at restaurants or events, which are known risk factors for Salmonella infection. Methods: A descriptive analysis using Salmonella surveillance data collected in Connecticut between 2015 to 2022 was performed to characterize the changes in travel and outside food exposures. Frequencies of exposures were compared before the pandemic, during the pandemic, and after the vaccine was implemented and restrictions eased. Rate ratios of observed to expected cases were calculated to explore trends through time. Possible changes in health-seeking behaviors, laboratory reporting, serotype distribution, and food consumption patterns were also explored. Results: During the pandemic, there were significant decreases in the proportion of Salmonella cases who traveled domestically (22.7% to 12.6%, p<0.01), traveled internationally (16.4% to 2.5%, p<0.01), ate food from food service establishments (65.8% to 57.9%, p<0.05), and ate food from events (19.9% to 9.5%, p<0.05). These exposures were associated with age (p<0.01). Cases ages 16-39 were most likely to travel and eat food away from home, consistent with the relative decrease in cases among this age group during the pandemic. There was no evidence suggesting that changes to health seeking behaviors, laboratory reporting, serotype distribution, or food consumption were driving factors in the overall decreased incidence. Conclusion: Changes to travel, restaurant dining, and event food exposures—due to COVID-19 public health interventions—are the most likely explanation for the observed decrease in Salmonella incidence during the pandemic.


This thesis is restricted to Yale network users only. It will be made publicly available on 05/10/2025