Transcript The Future is Nauseous: Salmonellosis in a Warmer and

Salmonellosis in a Warmer and Wetter Rhode Island
Gabriel Schwartz
Background
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.
Results
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.
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.
Manufacturing
(cleanliness)
Manufacturing
(contamination)
Production
Salmonella bacteria
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.
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.
Food Systems
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.
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.
Methods
Temperature data
National Climatic Data Center’s Quality Controlled Local
Climatological Data for Rhode Island from 2005 to 2012.
Distribution and
Delivery
Preparation and
Contamination
(restaurants and grocery
stores)
Preparation and
Contamination
(restaurants and homes)
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
Salmonella can infect food and ultimately humans in any part
of the route from production to consumption
on harvesting, shipping, and handling of food
may be an important locus of policy
intervention to adapt to a warmer world.
Takeaway Implications
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.
Health Data
Notification data from The Division of Infectious Disease
Epidemiology at the Rhode Island Department of Health, 20052012 (2012 data is preliminary).
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 twoweek lags for meteorological variables (e.g., average temperature one week ago)
were also included.
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
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.
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