Climate change data key to predicting future vector-borne disease outbreaks

The intersections of climate change and health were on full display at a Monday scientific session on the effects of climate change on arbovirus transmission in the Americas.

The global region has been facing big challenges related to arboviral diseases and, if predictions are correct, North America must prepare for more infections like those seen in the Miami- and Houston-area Zika outbreaks of 2016.

Arbovirus refers to any virus — Zika, chikungunya, dengue and yellow fever — transmitted by arthropod vectors like the Aedes mosquito. Since Zika’s first introduction to the Americas in 2015, it has affected more than half a million people. In February 2016, the World Health Organization declared Zika a Public Health Emergency of International Concern, given the number of microcephaly cases and other neurological disorders reported in Brazil.

As noted in the research of Andrea Vicari of the Pan American Health Organization, the Zika outbreak shifted the focus from the chikungunya virus, first reported in the region in 2013 and responsible for half a million infections in 2016 alone. Additionally, more than two million cases of dengue are reported in the region every year and the re-emergence of yellow fever are also cause for concern in South America. What accounts for these numbers, though? Researchers are turning to climate science for answers.

In her Annual Meeting presentation, Madeleine Thomson, senior research scientist at Columbia University’s International Research Institute for Climate and Society, said the recent release of the “Climate Science Special Report” from the U.S. Global Change Research Program makes it clear that the warming over the last century has happened and is human-caused.

“Now, if we can use the data to identify the environmental drivers of vector-borne disease, we can create modeling that predicts an outbreak,” she told attendees.

Temperature and rainfall are important drivers of arboviral disease transmission, affecting mosquito breeding sites as well as vector and virus development rates. Changes in climate are projected to increase global temperatures and the amount of heavy rainfall events in some regions, which can consequently increase the risk from arboviral diseases.

“Public health officials and climate experts must collaborate,” Thomson said. “We need to use climate information to improve the timing and targeting of our interventions, because the geographical distribution and number of cases is growing.”

According to Kristie Ebi, a professor at the University of Washington’s Department of Global Health, dengue is the world’s most important arboviral disease in terms of number of people affected.

“Over the past 50 years, incidence increased 30-fold: there were approximately 390 million infections in 2010,” she told session attendees. “Globalization, trade, travel, demographic trends and warming temperatures are associated with the recent spread of the primary vectors and the virus.”

Ebi noted that new geographic areas are becoming environmentally suitable for the mosquito’s lifecycle and for dengue transmission, with cases detected as far north as Toledo, Detroit and Toronto.

“The Aedes mosquito favors humans and will fly a mile to bite one,” Ebi said. “If anyone thinks we’re being paranoid, we have a right to be. Aedes really is out to get us. And the warmer it is, the shorter the time it takes to start and spread infection. It’s our responsibility to use environmental information to serve the people we’ve pledged to protect.”

One way APHA is offering real-life solutions to public health problems is through its work with the National Environmental Health Partnership Council. The partnership recently published the Environmental Health Playbook, which identifies opportunities for federal, state, local and tribal governments to adopt standard approaches that ensure environmental health equity, protections and access for all — particularly for vulnerable and at-risk populations. This includes protection from vector-borne disease.

Through prevention, response and case examples — such as the U.S. Zika virus outbreak, the Flint water crisis, Superstorm Sandy and Hurricane Katrina — the playbook demonstrates the need for and ways toward an effective, equitable and sustainable environmental health system that brings together all players to, as Ebi said, “serve the people we’ve pledged to protect.”