Climate Change Responsible for 19% of Today’s Rising Dengue Incidence Rates
A new study confirms the growing belief and evidence this vector-borne diseases will increase and see a greater burden globally.
This image shows the Aedes aegypti (yellow fever mosquito) is a carrier of the dengue virus and can transmit it to people.
According to a new study presented last week at the Annual Meeting of the American Society of Tropical Medicine and Hygiene, climate change is accounting for 19% of dengue cases currently.
And the study investigators says the environmental crisis has the potential to spark an additional 40%-60% spike in the next 25 years—by 2050 — and by as much as 150%-200% in some areas during this time period.
“We looked at data on dengue incidence and climate variation across 21 countries in Asia and the Americas and found that there is a clear and direct relationship between rising temperatures and rising infections,” said Erin Mordecai, PhD, an infectious disease ecologist at Stanford’s Woods Institute for the Environment and the study’s senior author. “It’s evidence that climate change already has become a significant threat to human health and, for dengue in particular, our data suggests the impact could get much worse.”1
Mordecai says the study was inspired after laboratory tests found mosquitoes that carry dengue progressively churn out more and more virus as temperatures rise within a specific range. She said this temperature-induced bump starts at about 20 degrees Celsius (68 degrees Fahrenheit), then intensifies before peaking at about 28 or 29 C (about 82 F).1
Mordecai’s team then looked at 21 dengue endemic countries, including Brazil, Peru, Mexico, Colombia, Vietnam and Cambodia, which regularly collect data on infection rates. They also looked at other factors that can affect dengue infection rates — like rainfall patterns, seasonal changes, virus types, economic shocks and population density — in order to isolate whether there was a distinct temperature effect.1
Mordecai said that dengue-endemic areas that are just now entering that 20 C to 29 C sweet-spot for virus transmission — parts of Peru, Mexico, Bolivia and Brazil — could face the biggest future risks, with infections over the next few decades rising 150% to 200%. She said the study probably underestimates the climate-related dengue threatbecause researchers were unable to predict potential climate impacts on dengue-endemic areas that have not consistently tracked infections, which includes large parts of sub-Saharan Africa and South Asia.1
Dengue’s Impact in the US
Typically, dengue has been viewed as more of an international problem, and there has been a small amount of infections. According to the Centers for Disease Control and Prevention (CDC) Most dengue cases reported in the 49 continental US states occur in travelers infected elsewhere. Local dengue transmission occasionally occurs in the continental United States. The federal agency says most local transmission of dengue in the United States happens in areas where dengue is common, like US territories and freely associated states.
However, it is important to note the incidences rates are starting to increase slowly, albeit in small amounts in the continental US. The CDC collects information on all cases in the US, and currently there has been 4,757 cases of locally acquired transmission3 with the following areas reporting cases:
- Puerto Rico: 4,536 cases
- Virgin Islands: 153 cases
- Florida: 53 cases
- California: 15 cases3
Mordecai said they were unable to quantify future impacts for areas like the southern regions of the continental United States, where dengue is just starting to emerge as a local threat. “But as more and more of the US moves into that optimal temperature range for dengue, the number of locally acquired infections will likely rise, though it’s too early to say how that will affect the global burden,” she said.1
A recent survey reinforces the concern of the medical community with this emerging risk. A new survey commissioned by the Abbott Pandemic Defense Coalition finds that 61% of respondents who were infectious disease professionals said mosquito-borne pathogens represent the greatest threat as the climate changes.4
Proactive Strategies
Contagion reported on the survey back in September, and the Abbott Coalition members involved in the survey offered some recommendations to manage local, regional, and global infectious disease outbreaks:
- The Need to Address Gaps: Public health systems need surveillance programs to quickly identify new pathogens and outbreaks using the diverse set of tools available. Funding for public health should be available to sustain these programs and help train the next generation of virus hunters who help identify and respond to outbreaks as well as educate the public on infectious diseases.
- Know What We’re Looking For: While every outbreak is important to understand, only some have the potential to spark national, regional or global health concerns. Understanding the profile that presents the most risk enables the healthcare community to calibrate efforts to protect public health. As viruses are discovered in new locations, it’s important for the medical community and the general public to know what viruses may be circulating, pointing to the need to continue strengthening surveillance and education efforts.
- Understand the Changing Environment: Experts are nearly unanimous in their view that the evolving way humans, animals and insects overlap and interact will change the dynamics of infectious disease outbreaks. Continued research and investments in new technology are needed to help understand how those dynamics are at play locally – old diseases in new regions, acceleration of routes of transmission – to help guide more effective preparation.4
