Enteric Disease Incidence in Georgia Following Extreme Rain and Drought Events Open Access
Noble, Emma (Spring 2022)
Abstract
Background The Georgia Department of Public Health participates in the Foodborne Diseases Active Surveillance Network (FoodNet) and conducts surveillance for nine enteric pathogens, four of which may have environmental routes of transmission. Current evidence suggests that extreme precipitation events may be associated with an increased incidence of enteric diseases. Current climate trends suggest an increase in the frequency and intensity of extreme precipitation events in coming decades due to climate change which could translate to an increase in enteric pathogen incidence. However, current literature lacks evidence for all enteric pathogens and tends to focus on salmonellosis incidence. To address this gap, we assessed the association between precipitation conditions and enteric disease incidence across four pathogens: Salmonella, Campylobacter, Cryptosporidium, and Shiga-Toxin Producing E. coli (STEC)
Methods Associations between precipitation and enteric disease incidence were estimated via Poisson regression models. Salmonellosis, campylobacteriosis, cryptosporidiosis, and STEC cases (N = 71,691) reported to the Georgia Department of Public Health between 2000 – 2019 for patients that did not travel internationally and were not linked to a known outbreak were included in analysis. Precipitation was defined for the conditions during the week of disease onset (7 days prior to onset date) and antecedent conditions (8-weeks prior to disease onset date, lagged by one week). Models controlled for time via season and year of disease onset and a county and year-specific population offset was used to account for population variation.
Results When examining precipitation data, a significant increase in disease incidence was observed among days with wet antecedent conditions and extreme, wet, and dry precipitation conditions the week of disease onset compared to days for which the antecedent and week of onset precipitation conditions were both classified as dry. The most notable increase occurred among days with wet antecedent conditions and dry week of precipitation conditions (IRR = 1.11, 95% CI: 1.08, 1.13). Days with wet antecedent and extreme or wet week of precipitation conditions also produced significant increases in enteric disease incidence (IRR = 1.04, 95% CI: 1.02, 1.07; IRR = 1.04, 95% CI: 1.01, 1.07). Days with dry antecedent conditions and wet week of precipitation conditions led to a significant decrease in enteric disease incidence (IRR = 0.96, 95% CI: 0.94, 0.99) as compared to days with both antecedent and week of precipitation conditions that were classified as dry. Disease-specific models showed similar trends with less precise confidence intervals due to smaller sample sizes.
Discussion This study suggests that antecedent precipitation conditions have a considerable influence on enteric disease incidence. The most notable increase in disease incidence occurs when there is a period characterized by high precipitation (wet antecedent conditions) followed by a brief dry period (dry week of precipitation) indicating there may be a combination of behavioral and environmental bacterial factors at play. The findings suggest there may be an increase in enteric disease incidence due to increased extreme weather-related events due to climate change.
Table of Contents
Table of Contents
Introduction 1
Methods 2
Precipitation Data 2
Health and Demographic Data 2
Statistical Analyses 3
Sensitivity Analyses 6
Results 7
Discussion 10
Conclusions 13
References 14
Table and Figures 17
Table 1: Case demographics 17
Table 2: Precipitation characteristics 18
Table 3: Overall association between enteric disease incidence and only short-term 19 (week of disease onset) or long-term (antecedent weeks) precipitation conditions.
Table 4: Overall and disease-specific association between enteric disease incidence and 20 the interaction of short-term (the week of disease onset) and long-term (antecedent
weeks) precipitation conditions.
Figure 1: Average annual county-level enteric disease incidence rate 21
Figure 2: Total number of county-level antecedent wet v dry days 22
Figure 3: Total number of county-level week of precipitation extreme v wet v dry days 23
Figure 4: Annual case count v average annual precipitation 24
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