Aedes aegypti mosquito. Source: Ohio Department of Health
As communities ward off mosquitoes this summer with layers of bug spray and citronella candles, researchers funded by the NOAA Climate Program Office’s International Research and Applications Project have launched a new monitoring and forecasting system to help prevent diseases carried by those pesky insects.
Led by Columbia University’s International Research Institute for Climate and Society and the Pan-American Health Organization, the system tracks places and times in the United States and neighboring regions when climate factors might enhance transmission of illnesses like Zika, dengue fever, and chikungunya spread by species of Aedes mosquitoes.
“This is the first system to monitor and forecast in real-time the conditions that are needed for transmission of Aedes-borne diseases,” said Ángel Muñoz, NOAA-funded climate scientist at Columbia University and lead author of the paper describing the system published in Nature Scientific Reports.
Called AeDES, the new system is expected to help public-health authorities identify at-risk areas at least a month ahead of time, improving response and planning operations.
“The advantage of AeDES is that health ministry staff working at the country and subnational level will be able to adapt forecasts to their specific localities, allowing field actions to be much more targeted and tailored to their local conditions,” said co-author and collaborator Ana Rivière-Cinnamond, from the Pan-American Health Organization. “Also, international and national health organizations could use the system to help identify future at-risk areas for...diseases at border areas, for example, so as to alert authorities in advance to take action.”
Real-time environmental suitability forecasts for dengue transmission in Central America, for July through September 2020. The map on the left presents the suitability of transmission with uncertainty shown in terms of probabilities (the percent chance of being above, below, or at normal) for each category: below normal (blue), normal (green), and above-normal (red). The map on the right presents the information in terms of the deterministic or expected environmental suitability index for transmission — values smaller than one indicate that environmental conditions are not suitable for disease propagation, and the larger the value the more suitable the conditions are. Source (Muñoz et al., 2020)
Aedes-transmitted diseases cause more than 50 million infections every year worldwide, including in the United States, and cases have increased by 30-fold in the last 50 years because of changes in changes in climate, land use and population.
The risk of disease outbreak goes up or down in part based on climate factors like temperature, rainfall and humidity, which affect the life and reproductive cycle of mosquitoes. According to the research team, the impact of climate on the presence of mosquitoes and viruses is one of the most important pieces of information for decision makers in the health sector to plan for and prevent outbreaks.
The map shows reported disease cases from mosquitoes in each U.S. state and territory from 2004 to 2016. According to the Centers for Disease Control and Prevention (CDC), recent outbreaks of Zika, chikungunya, and West Nile viruses point to the need for better tools to reduce the growing threat of these diseases in the United States. Source: CDC
Supercharged climate-health modeling
“We’ve combined multiple epidemiological models with multiple climate models, as well as seven decades of historical climate data,” Muñoz said.
When climate centers make forecasts of weather and climate, they often use ensembles of multiple models–which generate many simulations so as to give a range of possible outcomes.
Muñoz and his colleagues adapted this approach for AeDES, combining four well-known epidemiological models with the 96 climate models currently in the North American Multi-Model Ensemble. As a result, the team generates 384 simulations each time it runs AeDES.
“Because we have such a huge sample to draw from, the forecasts generated from these runs are really robust,” said Muñoz.
Results show that AeDES’ forecasting skill is very good, with ‘hotspots’ of higher skill in Guatemala, Honduras, El Salvador, Cuba, Haiti, Dominican Republic, Jamaica and Puerto Rico. Decision makers can leverage the enhanced skill in those regions for better prevention and control strategies.
Public-health specialists can also use AeDES to calculate and visualize the environmental suitability of disease transmission month-by-month going back to 1948, allowing them to assess trends and better understand how climatic changes have been impacting different regions.
“This research contributes to the potential reduction of health related impacts through the use of climate information and early warning systems,” said Lisa Vaughan, NOAA International Research and Applications Project Program Manager who funded the research. “It will help identify spatial and temporal risk in order to tailor interventions and policies.”
This research was partially supported by ACToday, the first Columbia World Project, as well as by grants from the NOAA Climate Program Office’s International Research and Applications Project, the National Science Foundation, the National Institutes of Health and the Swedish Research Council.
This story was adapted from a press release written by Columbia University’s International Research Institute for Climate and Society. Read the press release here.