An estimated 1.2 million salmonellosis cases occur in the United States annually. Salmonella serotype Enteritidis (SE) accounts for 20% of salmonellosis cases reported to the Foodborne Diseases Active Surveillance Network (FoodNet), which conducts active population-based surveillance in 10 sentinel sites. The incidence of SE infection is higher in rural areas, although the role rurality plays in source of infection is unclear. We analyzed exposure data to better understand how sources of SE infection differ by rurality.
METHODS:
We compared food and environmental exposures among SE patients to patients infected with other serotypes (non-SE) who were reported to FoodNet during January 2014–December 2015. We used Rural-Urban Continuum Codes to define rurality as metropolitan or non-metropolitan. We calculated odds ratios (aOR), adjusted for season during which illness occurred, for each category. We excluded patients aged <1 year, associated with an outbreak, or who reported international travel in the 7 days before illness onset.
RESULTS:
During 2014–2015, FoodNet collected exposure histories from 1,342 SE patients and 5,196 non-SE patients. Among these, 1,119 (83%) SE and 4,054 (78%) non-SE patients lived in metropolitan areas and 223 (17%) SE and 1,142 (22%) non-SE patients in non-metropolitan areas. Among metropolitan patients, SE patients were more likely to have consumed any chicken (aOR=1.5; p<0.01, 80% SE patients vs. 73% other serotype patients), chicken outside the home (aOR=1.4; p<0.01, 47% vs. 39%), beef (aOR=1.2; p=0.03, 66% vs. 62%), beef outside the home (aOR=1.2; p=0.02, 33% vs. 29%), turkey outside the home (aOR=1.5; p<0.01, 12% vs. 9%), any seafood (aOR=1.2; p=0.02, 23% vs. 19%), raw or uncooked seafood (aOR=1.6; p=0.01, 5% vs. 3%), fish (aOR=1.2; p=0.03, 30% vs. 27%), eggs outside the home (aOR=1.4; p<0.01, 19% vs. 15%), spinach (aOR=1.3; p<0.01, 22% vs. 18%), and lettuce (aOR=1.4; p<0.01, 56% vs. 48%) than non-SE patients. Among non-metropolitan patients, SE patients were more likely to have consumed runny eggs (aOR=1.5; p=0.04, 18% vs. 12%), dairy (aOR=1.8; p=0.01, 83% vs. 74%), and lettuce (aOR=1.9; p<0.01, 53% vs. 38%) than non-SE patients.
CONCLUSIONS:
Several foods, but not environmental factors, were associated with SE infection in both metropolitan and non-metropolitan areas and food types differed by area. Many foods consumed outside of the home were associated with SE infection among metropolitan patients, while none were associated among non-metropolitan patients. The differences in settings of exposure combined with differences by area highlight important issues to consider when designing location-specific evidence-based control measures.