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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Environmentally Integrated Dairy Management Research » Research » Publications at this Location » Publication #341294

Research Project: Improving Nutrient Use Efficiency and Mitigating Nutrient and Pathogen Losses from Dairy Production Systems

Location: Environmentally Integrated Dairy Management Research

Title: Understanding outbreaks of waterborne infectious disease: quantitative microbial risk assessment vs. epidemiology

item Burch, Tucker

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/21/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Drinking water contaminated with microbial pathogens can cause outbreaks of infectious disease, and these outbreaks are traditionally studied using epidemiologic methods. Quantitative microbial risk assessment (QMRA) can predict – and therefore help prevent – such outbreaks, but it has never been rigorously validated against epidemiologic measurements. My objective was to compare the two approaches using data from reported waterborne outbreaks of gastrointestinal disease. I screened 2000 papers and identified ten outbreak reports that supplied the necessary data: responsible pathogen, attack rates measured using epidemiologic methods, and pathogen concentrations measured in the source water. All ten outbreaks involved treated public drinking water supplies; seven outbreaks were caused by Cryptosporidium and three by Giardia. The QMRA accounted for daily drinking water intake, outbreak duration, and used published dose-response models for both organisms. QMRA predictions correlated well with epidemiological measurements at an order-of-magnitude scale. For nine of 10 data points, QMRA predicted the measured attack rate (cases per person per outbreak) within an average factor of 6.1 (range = 1.2 to 17), while the remaining data point was off by a factor of 780. There was no systematic bias in QMRA predictions compared to epidemiological measurements; QMRA over-predicted attack rates for five outbreaks and under-predicted them for five. These results demonstrate that QMRA and epidemiology can produce equivalent estimates of disease rates for waterborne Cryptosporidium and Giardia, and that QMRA can be used as a valid complement to traditional epidemiologic methods for understanding and preventing outbreaks of waterborne infectious disease.