Date of Award

January 2013

Document Type

Open Access Thesis

Degree Name

Master of Public Health (MPH)

Department

School of Public Health

First Advisor

James Hadler

Abstract

Background: Shiga toxin Escherichia coli (STEC) O157 and other STEC strains are a well-known cause of enteric illness. National estimates are that STEC O157 causes approximately 96,534 illnesses every year in the United States, with another 168,698 illnesses caused by non-O157 STEC serotypes. Determining economic and sociodemographic factors associated with enteric disease incidence may provide new understandings of the transmission of these illnesses, particularly community transmission, and may prove useful in the prevention of disease.

Methods: A total of 764 incident STEC cases were reported in CT from 2000 to 2011. Incident cases were geocoded based on the case's address using ArcGIS. Incident cases were linked to neighborhood poverty level and neighborhood rurality level at the census tract level. Neighborhood poverty level was broken down into four categories for analysis: 0 - 4.99%, 5 - 9.99%, 10 - 19.99%, and greater than 20% of the population in the census tract living below the federal poverty line. Neighborhood rurality level was broken down into quartiles for analysis as well: 0 - 24.9%, 25 - 49.9%, 50 - 74.9%, and greater than 75% of housing units in the census tract considered rural. Twelve-year age-adjusted Shiga toxin E. coli incidence rates were calculated for each poverty category and each rurality category. Incidence rates were also determined by race/ethnicity.

Results: Of the 764 cases, 744 (97.4%) were able to be geocoded. Both neighborhood level poverty and neighborhood level rurality were found to be significantly associated with STEC incidence. Age-adjusted rates of all STEC infections revealed a trend of decreasing neighborhood poverty level and increasing STEC incidence (p<0.001); residents of the wealthiest census tracts were four times as likely to contract STEC compared to residents of the highest poverty census tracts. Age-adjusted rates of all STEC infections showed a trend of increasing neighborhood rurality and increasing incidence (p<0.001); residents of the most rural census tracts were 1.7 times as likely to contract STEC compared to residents of the most urban census tracts The same significant incidence associations were seen among O157 STEC cases and non-O157 STEC cases separately and were consistent across time periods, age, and race/ethnicity groups.

Conclusions: STEC incidence decreased as neighborhood poverty increased, showing a dose-response relationship with socioeconomic status, and increased as neighborhood rurality increased. These findings can be used to more effectively target education and interventions, especially in high-income neighborhoods, which include more rural neighborhoods in Connecticut. Area-based socioeconomic measures provide additional insights into the epidemiology of infectious diseases and can be used further to elucidate possible control and prevention measures. Future study implications include the need to better understand what risk exposures are driving the differences between higher and lower poverty areas, including among infants and children. What types of educational efforts are effective at reducing risk among those of higher SES also needs to be investigated. This analysis provides support that community-level risk factors play a larger role in the transmission of STEC.

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This is an Open Access Thesis.

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