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Upstate study: Climate change likely exacerbated Zika outbreak after 2016 Ecuador earthquake

A Zika virus outbreak in coastal Ecuador in 2016 was likely worsened by a strong El Niño and a magnitude 7.8 earthquake that struck the region in April of that year, according to a new study by Anna Stewart Ibarra, PhD, MPA, Upstate Medical University, and led by Cecilia Sorensen, MD, University of Colorado School of Medicine.

Commentary on the study was published Sept. 11 in GeoHealth, a journal of the American Geophysical Union. The commentary states that the earthquake left more people exposed to disease-carrying mosquitoes, and climate variability associated with the 2014-2016 El Niño event created more favorable mosquito breeding grounds.

The researchers found that increasing temperatures associated with a strong El Niño event, combined with destruction of the region’s infrastructure and a population influx into large cities, likely caused the number of Zika cases to increase 12-fold in just three months.

Prior research by Stewart Ibarra and colleagues established a link between the 2014-2016 El Niño and the spread of Zika in South America, but this new study goes further and examines the interaction between these two events and the 2016 earthquake.

“Global changes have led to the emergence and persistence of mosquito-borne viruses such as Zika,” says Stewart Ibarra, an internationally recognized expert in the ecology of infectious diseases, director of the Latin America Research Program at Upstate’s Center for Global Health & Translational Science and a faculty member in Upstate’s Department of Medicine. “Our previous studies have found that extreme events, such as drought and flooding, can escalate the potential for increased mosquito-borne infections. We must now factor in earthquakes and other natural disasters as we work toward creating a more comprehensive plan to prevent the spread of these viruses.”

This most recent article suggested that changes in the climate could amplify the effects of natural disasters and disease outbreaks in socially vulnerable regions. “Areas that are already stressed by short-term climate changes like El Niño can be sent over the edge due to a catastrophe and may struggle to recuperate afterwards,” said Sorensen, a Living Closer Foundation fellow in climate and health policy at the University of Colorado School of Medicine.

The researchers studied the effects of short-term changes in Ecuador’s climate, not long-term global warming patterns. But extreme El Niño events such as the one observed in 2016 are projected to increase in frequency, say the researchers, due to human-caused climate change. The team suspects that the combination of increased extreme events and long-term warming could lead to conditions that favor the spread of mosquito-borne diseases.

A magnitude 7.8 earthquake struck the province of Manabi in coastal Ecuador on April 16, 2016. The quake affected approximately 720,000 people, destroyed much of the region’s sanitation and health care infrastructure, and resulted in a massive influx of displaced residents into urban areas.

Stewart Ibarra led the development of a mobile health clinic in the days following the earthquake, which has since evolved into the non-governmental organization Walking Palms Global Initiative, founded by Avriel Diaz (co-author on this study) and David Madden. They saw many women and children coming in with symptoms typical of mosquito-borne illnesses like dengue fever and Zika. In July 2016, UNICEF reported that the number of Zika cases in Ecuador spiked from 92 cases before the earthquake to 1,106 cases just three months after the event. Eighty-five percent of the cases of Zika in Ecuador in 2016 occurred in Manabi Province, the site of this study, located near the earthquake epicenter.

The research team studied how damage from the earthquake and short-term changes in weather associated with El Niño could have potentially exposed more people to mosquitoes and exacerbated the outbreak.

“We saw so many people affected by the earthquake that were sleeping outside without any shelter from mosquitoes, so we were worrying that the region’s changing climate could facilitate the spread of diseases,” Sorensen said. “Natural disasters can create a niche for emerging diseases to come out and affect more people.”

They suggest that El Niño created ideal climate conditions for Zika-carrying mosquitos. The warmer air temperatures brought by El Niño have previously been associated with a higher likelihood of dengue outbreaks. Warmer temperatures can accelerate viral replication in mosquitoes and influence mosquitos’ development and breeding habits.

The team also believes an increase in water scarcity after the earthquake indirectly benefited mosquito development. The quake damaged municipal water systems, forcing people to store water in open containers outside their homes. These containers served as additional habitats for mosquito larvae to grow.

Joining Stewart Ibarra and Sorensen in the study are Mercy J. Borbor-Cordova, PhD, Faculty of Naval Engineering, Oceanic Sciences and Natural Resources, Edcuela Superior Politecnica del Litoral, Guayaquil, Ecuador; Avriel Diaz, Department of Evolution, Ecology and Environmental Biology, Columbia University, New York; and Jay Lemery, MD, Department of Emergency Medicine, University of Colorado School of Medicine Aurora, CO.

Visit “Climate variability, vulnerability, and natural disasters: A case study of Zika virus in Manabi, Ecuador following the 2016 earthquake,” for study details.

Caption: Anna Stewart Ibarra, PhD, MPA, right, is shown registering people seeking medical care at the Sathya Sai School in Bahia de Caraquez, following the 2014 earthquake in Ecuador.

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