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Salmonellosis in a Warmer and Wetter Rhode Island Gabriel Schwartz Background Results Food Systems Takeaway Implications Salmonellosis is an infection caused by Salmonella bacteria. Salmonella causes over one million illnesses each year, and causes more hospitalizations and deaths than any other food-borne microbe. Since 1980, there have been 789 major outbreaks worldwide, more than any other disease. About 42,000 cases of salmonellosis are reported annually in the U.S., though due to underreporting, the actual number of cases may be up to 29 times greater. Laboratory studies show that there is a positive relationship between temperature and salmonella replication. Methods Salmonella begins its life cycle in the small intestine of the human body. Symptoms usually appear within 12-72 hours and severe cases must be treated by antibiotics. Salmonella bacteria Production Manufacturing (cleanliness) Manufacturing (contamination) Distribution and Delivery Preparation and Contamination (restaurants and grocery stores) Preparation and Contamination (restaurants and homes) Salmonella can infect food and ultimately humans in any part of the route from production to consumption Temperature data National Climatic Data Center’s Quality Controlled Local Climatological Data for Rhode Island from 2005 to 2012. Health Data Notification data from The Division of Infectious Disease Epidemiology at the Rhode Island Department of Health, 2005-2012 (2012 data is preliminary). The various meteorological variables studied here appear to have distinct effects on Salmonellosis cases across time, perhaps reflecting differing impacts of weather at various points In the food system. Broad consensus across a variety of sources is that Southern New England will experience an increase in temperature, humidity, and rainfall, though the latter is predominantly during the winter months, and may even decrease during the summer. The results presented here indicate that the future of gastrointestinal disease in RI relies on an interaction of all three of these variables. A slight increase in precipitation may offset the exacerbating effects of increased temperature and humidity on the number of Salmonellosis cases in RI, though this relationship remains tenuous. Alternatively, humidity and temperature may rise much more precipitously than precipitation, especially during the summer, when Salmonellosis is most prevalent and dangerous. Hotter and more humid summers in RI would be particularly brutal if the risk of dehydration from heat was multiplied by an increased danger of contracting a dehydrating gastrointestinal infection. As the planet continues to warm with climate change, Salmonellosis may continue to increase in prevalence, resulting in greater costs to quality of life and greater economic costs from treatments and hospitalizations. Much more research needs to be done on the relationship between salmonellosis and climatic variables, as this study suggests that disease prevalence is due to complex interactions between the climate, human behavior, and microbiotic communities. Statistical Analysis Multivariate Poisson regression was used to estimate the effects of meteorological variables (weekly averages) on weekly sums of the number of Salmonellosis cases in RI, controlling for outbreaks, population growth, past Salmonellosis cases, and time, both seasonally and across years. One- and two-week lags for meteorological variables (e.g., average temperature one week ago) were also included. Past studies have indicated dramatic effects. A 1° C increase in temperature was associated with a 15% increase in Salmonellosis notifications within a single month in New Zealand, consistent with previous studies from around the world. However, very few of those studies account for precipitation, and none account for humidity. Especially given that disease ecology varies across geographies, the relationship between salmonellosis and climate remains vastly understudied. This study examined the relationship between meteorological variables (temperature, precipitation, and relative humidity) and foodborne illness. Salmonellosis was a natural focus, due to data availability, its large impact on human health, and the substantial but insufficient depth of existing knowledge about its disease ecology. The CDC provides information on their website and helpful information to stop the prevention of Salmonella, such as an e-card to send to family and friends. The number of Salmonellosis cases in RI are plotted below against the most significant and interesting meteorological variables. Multivariate relationships, which more accurately reflect reality, are presented in the regression output table to the bottom left. Image Citations: Salmonella bacteria photo: http://www.fas.org/programs/bio/factsheets/salmonella.html Salmonella Infection photo: http://www.rayur.com/salmonellosis-salmonella-enteritis.html NCDC logo: http://www.erh.noaa.gov/pbz/new_climate.html RI Department of Health logo: http://www.mhri.org/ss_plugins/content/content.php?content.2261 Food production to table photo: modified from http://www.cdc.gov/vitalsigns/FoodSafety/Farm_to_table.html Make Food Safer to Eat Ecard: http://t.cdc.gov/ecards/message.aspx?cardid=561 Serious Eats: http://www.seriouseats.com/images/20100528-farmfreshRI3.jpg Acknowledgements I would like to extend special thanks to: ⋄ Justin Dittmeier, ’13; Natalie Villacorta, ‘13; Cody Zeger, ‘14; and Eunice Lee, ‘14. ⋄ Lynn Carlson, Geographic Information Systems Manager, Center for Environmental Studies, Brown University ⋄ Michael Gosciminski, Department of Infectious Disease Epidemiology at Rhode Island Department of Health ⋄ Stephen McGarvey, PhD, MPH, Professor of Epidemiology, Brown University ⋄ J. Timmons Roberts, PhD, Professor of Environmental Studies and Sociology, Brown University ⋄ Katherine Smith, PhD, Assistant Professor of Ecology and Evolutionary Biology, Brown University The food consumed in RI often arrives through an array of (inter)national channels, meaning that the climatic conditions under which food in RI is grown are dramatically diverse and difficult to track. Nonetheless, regulations on harvesting, shipping, and handling of food may be an important locus of policy intervention to adapt to a warmer world.
