Crosson, William

Ernst, Kacey

Monaghan, Andrew

Morin, Cory

Quattrochi, Dale

NASA Technical Reports Server

Spatial Disparities in Dengue Risk along the 
US-Mexico Border
Cory Morin1
Andrew Monaghan2
Kacey Ernst3
William Crosson4
Dale Quattrochi1
1NASA – Marshall Space Flight Center, Huntsville, AL
2National Center for Atmospheric Research, Boulder, CO
3University of Arizona, Tucson, AZ
4Universities Space Research Association/Science and Technology Institute, Huntsville, AL
https://ntrs.nasa.gov/search.jsp?R=20150018443 2019-08-31T06:30:17+00:00Z
Mosquito-borne Disease Ecology
• Annually ~96 million 
cases of disease world 
wide
• Endogenous 
transmission in Florida + 
Texas
• Symptoms: muscle and 
bone ache, fever, and 
hemorrhagic 
manifestations in rare 
cases
• 4 serotypes of virus
Dengue VirusWest Nile Virus
Main Cycle
Main Cycle
Accidental
Mosquito Life Cycle
Environment - Vector - Virus Connections
Modeling Dengue Fever in Sonora, Mexico
• Dengue ecology
• Mosquito population dynamics
• Virus transmission dynamics
• Aedes aegypti mosquitoes
• Urban, container breeding
• Live in tropical habitats
• Anthropophilic 
• Sonora Mexico
• Arid climate
• Monsoon precipitation
• Seasonal cycles of dengue transmission
• Large annual variations in epidemics www.sigfridoaguilar.org
Data and Methods
• Study area
• 4 sites in Sonora, Mexico
• Meteorological/Dengue case data
• Daily maximum and minimum temperatures (NLDAS)
• Daily precipitation (TRMM, NLDAS) 
• Weekly suspected dengue cases by city 2006-2011
• Model
• Parameterized for Aedes aegypti mosquitoes, daily 
time step 
• Run from 2005-2011 under varying parameters (500)
• Best 3% of runs chosen by comparison with 
suspected case data (R^2)
Geo-mexico.com
Model Parameter Estimation
• Containers
• Based on household surveys (Hermosillo)
• Human managed and open containers
• Used mean values and +/- 25% and 50%
• Minimum infectious rate
• Minimum amount of infectious humans 
• Maintains virus within the population
• Based on case data and previous study in San Juan, PR 
• Maximum larval density
• Used to calculate density-dependent mortality
• Based on observations, literature, and previous 
study in San Juan, PR
answers.yahoo.com
Mosquitoeater.com            beingalison.comDC.gov
Modeling Aedes aegypti and Dengue Virus 
Ecology
Dengue and Climate Comparisons
Very SimilarVery Similar
Variable
Epidemics 
asynchronous
Dengue Precipitation
Max Temp Min Temp
Climate, Dengue, Simulations: Hermosillo
• 2008 and 2010 are largest 
dengue years
• Epidemics follow monsoon 
rains
• Precipitation magnitude not 
correlated with dengue case 
incidence
• Introduction rate is likely 
important
Climate, Dengue, Simulations: Guaymas
• Dengue is highest in 2010 
despite dry conditions
• Similar to Hermosillo
• Driest city examined
• Importance of human 
managed water sources
• Model has difficulty 
simulating seasons with no 
peak
• 2008 + 2011
Climate, Dengue, Simulations: C. Obregon
• Lowest annual variability in 
dengue cases
• Model has difficulty 
simulating seasons with no 
peak
• 2011
Climate, Dengue, Simulations: Navojoa
• 2008 is highest dengue year
• Dengue transmission is low 
in 2010
• Unlike Hermosillo and 
Guaymas
• Model has difficulty 
simulating seasons with no 
peak
• 2006, 2007, and 2010
Dengue Transmission in Nogales
• Why is there little/no dengue 
transmission in nearby Nogales?
• Hypothesis: Climate conditions are 
cooler
• Suppression of mosquito population
• Extension of extrinsic incubation period 
(EIP)
• Experiments:
• 1: Rerun Hermosillo simulations with Nogales meteorological data
• 2: Perform experiment 1 with 1°C warming
• Performed during large epidemic years (2008 and 2010)
Hermosillo/Nogales Comparison: Mosquitoes
• Little/no dengue is 
simulated under Nogales 
meteorological conditions
• With warming, the 
mosquito population is 
higher under Nogales 
conditions in 2010
• Results in increased virus 
transmission
• With warming, there is a 
modest mosquito 
population increase in 2008
• No dengue
Hermosillo/Nogales Comparison: EIP
• EIP is considerably longer 
under Nogales conditions
• Under Nogales conditions, 
the EIP is longer during the 
transmission season in 2008
• Prevents completion of EIP 
during mosquito lifetime
• EIP shortened under 1°C 
warming conditions
• Especially during 
transmission season
Challenges in Climate and Health Research
• Reporting problems
• Misdiagnosis
• Subclinical cases
• Reporting errors/bias
• Availability of data
regblog.org
• Human vs. climate influences
• Socioeconomic status
• Microclimatic influences
• Human adaptions to climate
• Knowledge gaps
• Incubation periods
• Transmission probabilities
• Evolution and adaption of 
virus and human immunity
virology.wisc.edu
CDC.gov
Conclusions
• Nearby locations can exhibit very different patterns of dengue transmission
• Differences in virus introduction
• Small climatic differences can make large differences
• Dengue epidemics follows monsoon rains
• Timing is consistent, however, the magnitude is not well correlated
• Climate is an important regulator of dengue transmission in Nogales
• Affects mosquito population dynamics and the virus incubation period
• Year to year variability is important
• Dengue transmission dynamics in northern Mexico may affect dengue risk in the United 
States
• Travel, climate change
• Recent dengue epidemic in Nogales
Next Steps
• Run model for additional 
locations along 
US/Mexico border
• Does transmission vary?
• Why?
• Perform fine scaled 
model runs
• How does risk vary within 
a city?
• Consider socioeconomic 
conditions in model
Thank You for Your Attention!
Questions?


Spatial Disparities in Dengue Risk Along the US-Mexico Border

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server