Author(s): Csaba Varga 1,2,*, Patience John 2, Martin Cooke 2,3, Shannon E. Majowicz 2
Nontyphoidal Salmonella enterica (NTS) is responsible for an estimated 150,716 illnesses, 1,565 hospitalizations, and 29 deaths each year in Canada, of which the majority are foodborne . On a worldwide level, diarrheal and invasive infections caused by NTS have the highest yearly disease burden among all foodborne infections, with 4.07 million attributable Disability Adjusted Life Years . Among the more than 2,600 currently known NTS serotypes, only a small portion cause human infection, most commonly gastroenteritis [3,4]. In Canada, NTS serotype Enteritidis (S . Enteritidis), Typhimurium ( S . Typhimurium), and Heidelberg ( S . Heidelberg) are the most frequent serotypes, consisting of over 50% of all serotypes detected . Despite constant attempts to decrease the incidence of NTS infections during the last decade, public health authorities have not been successful, due, in part, to the significant increase in infections with certain serotypes, such as S . Enteritidis [3,4,6].
Salmonellosis is a complex disease with a multitude of factors that influence its morbidity and mortality. Specific serotypes are likely to be linked to particular transmission routes based on their role in natural ecosystems . Previous studies have described common food exposure sources for NTS infections with different serotypes. Salmonella Enteritidis was most commonly associated with the consumption of chicken, eggs, turkey and sprouts, S . Typhimurium with beef, dairy, pork and vegetables, and S . Newport with fruits and vegetables . While the majority of NTS infections are foodborne, contact with infected animals or their contaminated environments should not be overlooked as an infection source since NTS are frequently carried asymptomatically by food animals or pets .
Studying infectious diseases in cities is increasingly important , considering the growth of urban populations, which are expected to exceed 60% of the total global population by 2050 . Our study was conducted in the city of Toronto, the capital of the province of Ontario and the largest city in Canada, situated along Lake Ontario's northwestern coast.
According to the 2016 Census, Toronto had a population of 2,731,571 . Toronto's neighborhoods are diverse, and the spatial heterogeneity of salmonellosis rates may occur from variations in underlying local socioeconomic, demographic and environmental risk factors [12,13]. Identifying geographical areas with significantly higher or lower serotype-specific infection rates can offer valuable etiological indicators to guide the development of public health prevention and control programs to reduce the health burden of NTS infections .
Recent studies have applied a number of spatial epidemiological methods to identify spatial clusters of NTS infections with various serotypes, including S . 1,4, ,12:i:- in Portugal , S . Enteritidis in Canada [13,14], S . Napoli in Italy , and S . Wangata and S . Typhimurium in, Australia .
With the expansion of technological capabilities in geographic information systems (GIS) and disease mapping along with the growing power of applied spatial epidemiological methods, several recent studies have used these methods to understand the spread and area-level risk factors of various infectious diseases , including granulocytic ehrlichiosis ,...