Spatial and space-time clustering and demographic characteristics of human nontyphoidal Salmonella infections with major serotypes in Toronto, Canada

PLoS One. 2020 Jul 1;15(7):e0235291. doi: 10.1371/journal.pone.0235291. eCollection 2020.

Abstract

Nontyphoidal Salmonella enterica (NTS) causes a substantial health burden to human populations in Canada and worldwide. Exposure sources and demographic factors vary by location and can therefore have a major impact on salmonellosis clustering. We evaluated major NTS serotypes: S. Enteritidis (n = 620), S. Typhimurium (n = 150), S. Thompson (n = 138), and S. Heidelberg (n = 136) reported in the city of Toronto, Canada, between January 1, 2015, and December 31, 2017. Cases were analyzed at the forward sortation area (FSA)-level (an area indicated by the first three characters of the postal code). Serotype-specific global and local clustering of infections were evaluated using the Moran's I method. Spatial and space-time clusters were investigated using Poisson and multinomial scan statistic models. Case-case analyses using a multinomial logistic regression model was conducted to compare seasonal and demographic factors among the different serotypes. High infection rate FSAs clustered in the central region of Toronto for S. Enteritidis, in the south-central region for S. Typhimurium, in north-west region for S. Thompson, and in the south-east region for S. Heidelberg. The relative risk ratio of S. Enteritidis infections was significantly higher in cases who reported travel outside of Ontario. The relative risk ratio of infections was significantly higher in summer for S. Typhimurium, and in fall for S. Thompson. The relative risk ratio of infection was highest for the 0-9 age group for S. Typhimurium, and the 20-39 age group for S. Heidelberg. Our study will aid public health stakeholders in designing serotype-specific geographically targeted disease prevention programs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Cluster Analysis
  • Demography
  • Female
  • Geography
  • Humans
  • Infant
  • Infant, Newborn
  • Male
  • Middle Aged
  • Ontario / epidemiology
  • Risk Factors
  • Salmonella Food Poisoning / epidemiology*
  • Salmonella Food Poisoning / microbiology*
  • Salmonella enterica / classification*
  • Salmonella enterica / isolation & purification*
  • Seasons
  • Serogroup
  • Space-Time Clustering
  • Young Adult

Grants and funding

CV was supported by a start-up fund of the Department of Pathobiology, College of Veterinary Medicine, University of Illinois at Urbana-Champaign. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.