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On November 5, 2015, a privately owned tailings dam located in the city of Mariana, in Brazil, collapsed, releasing around 60 million cubic meters of iron waste. This large volume of toxic mud poured into the Doce River and flowed along 600 kilometers of the river, causing mudflows that contaminated the river and even the coast near its estuary in the Atlantic Ocean. It was the worst global disaster of its kind since the 1960s. The catastrophe caused significant environmental damage. Part of the fauna and flora were immediately destroyed and, because the contamination was so severe, many species of plants and animals have not recovered. The disaster may also have led to an increase in transmission of vector-borne diseases. Diseases like dengue fever, Chikungunya, Zika and yellow fever are of public health significance in Brazil. They are caused by arboviruses transmitted to humans through the bite of the domestic mosquito Aedes aegypti. The goal of this study was to investigate a causal relationship between the Mariana dam disaster and the occurrence of these four diseases in the affected region. I sought to collect data for the occurrence of vector-borne diseases before and after the disaster, making comparisons between municipalities that were affected by the disaster and a group of control ones. The main research question I addressed was: Did the Mariana dam disaster cause an increase in the occurrence of arboviral diseases in the affected area, when compared to control areas? In order to answer this question I tested if the Mariana dam disaster increased the occurrence of arboviral infections in the affected area more significantly than in regions not affected by the disaster. In order to test the relationship between the occurrence of the diseases and the disaster, I used data obtained from the DATASUS database, including notified cases, outpatient visits, hospital admissions and deaths linked to the four diseases. Data from 2011 to 2015 provided values for cumulative occurrences before the dam break, for affected and control municipalities, while data from 2015 to 2019, for the period after the disaster. Using these data, I obtained the attributable risk, the risk ratio and the percent change before and after the disaster, for affected and control municipalities. Then I conducted time series analysis and generated graphs for cumulative occurrences. The results obtained showed that, after the disaster, there was an increase in the health indicators related to two diseases, Chikungunya and yellow fever, in the affected municipalities as compared to the control group. For both diseases, the values presented were concordant among all databases with available data. For dengue, on the other hand, it was not possible to confirm the specific hypothesis, meaning, I could not confirm that the increase on dengue fever occurrence was higher in the affected region than in similar regions not affected by the disaster. For Zika, data were not available for the period preceding the disaster, so investigation of the research hypothesis could not be conducted. Therefore, the data analyzed in this study suggests that the Mariana dam disaster increased the occurrence of some arboviral infections in the area affected by the disaster.

On November 5, 2015, a privately owned tailings dam located in the city of Mariana, in Brazil, collapsed, releasing around 60 million cubic meters of iron waste. This large volume of toxic mud poured into the Doce River and flowed along 600 kilometers of the river, causing mudflows that contaminated the river and even the coast near its estuary in the Atlantic Ocean. It was the worst global disaster of its kind since the 1960s. The catastrophe caused significant environmental damage. Part of the fauna and flora were immediately destroyed and, because the contamination was so severe, many species of plants and animals have not recovered. The disaster may also have led to an increase in transmission of vector-borne diseases. Diseases like dengue fever, Chikungunya, Zika and yellow fever are of public health significance in Brazil. They are caused by arboviruses transmitted to humans through the bite of the domestic mosquito Aedes aegypti. The goal of this study was to investigate a causal relationship between the Mariana dam disaster and the occurrence of these four diseases in the affected region. I sought to collect data for the occurrence of vector-borne diseases before and after the disaster, making comparisons between municipalities that were affected by the disaster and a group of control ones. The main research question I addressed was: Did the Mariana dam disaster cause an increase in the occurrence of arboviral diseases in the affected area, when compared to control areas? In order to answer this question I tested if the Mariana dam disaster increased the occurrence of arboviral infections in the affected area more significantly than in regions not affected by the disaster. In order to test the relationship between the occurrence of the diseases and the disaster, I used data obtained from the DATASUS database, including notified cases, outpatient visits, hospital admissions and deaths linked to the four diseases. Data from 2011 to 2015 provided values for cumulative occurrences before the dam break, for affected and control municipalities, while data from 2015 to 2019, for the period after the disaster. Using these data, I obtained the attributable risk, the risk ratio and the percent change before and after the disaster, for affected and control municipalities. Then I conducted time series analysis and generated graphs for cumulative occurrences. The results obtained showed that, after the disaster, there was an increase in the health indicators related to two diseases, Chikungunya and yellow fever, in the affected municipalities as compared to the control group. For both diseases, the values presented were concordant among all databases with available data. For dengue, on the other hand, it was not possible to confirm the specific hypothesis, meaning, I could not confirm that the increase on dengue fever occurrence was higher in the affected region than in similar regions not affected by the disaster. For Zika, data were not available for the period preceding the disaster, so investigation of the research hypothesis could not be conducted. Therefore, the data analyzed in this study suggests that the Mariana dam disaster increased the occurrence of some arboviral infections in the area affected by the disaster.