Brazil Faces Deadly Dengue Outbreak in the Face of Global Warming

A health worker sprays insecticide in an effort to kill dengue-bearing mosquitoes in Brasilia, the capital of Brazil.

Photo Credit: REUTERS/Ueslei Marcelino

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Brazil experienced record outbreaks of dengue fever in late 2023, and cases are only expected to increase throughout 2024. The mosquito-borne disease with a fatality rate of up to 15% (depending on the speed of treatment) has been ripping through South and Central America, and has even presented cases in areas that have never before been affected by the virus, such as France and California. Brazil’s Health Ministry predicted 4.2 million outbreaks of the virus in the country for this year alone. For reference, the Pan-American Health Organization only recorded 4.1 million cases for all 42 countries in the region in 2023. Four Brazilian states have declared states of emergency, including Rio de Janeiro and the federal district. This epidemic presents a danger not only to Brazil, which is under-equipped for such an outbreak, but also for neighboring countries and continents. 

The surge in dengue cases has led to a shortage of the virus’s primary vaccine, Qdenga, as the supplier, Japan’s Takeda Pharmaceuticals, is scrambling to keep up with demand. Brazil purchased 5.2 million doses for 2024 and 9 million for 2025. Additionally, Takeda donated another 1.3 million doses. Despite these numbers, there are still not enough vaccines to cover all of the at-risk populations in Brazil, much less the rest of the world. While the dengue virus can affect individuals of all demographic categories, it is primarily dangerous to children and the elderly. Brazil has started a campaign to vaccinate all children between the ages of 10 and 14 with the hopes that citizens who most need medical intervention will receive it before it is too late. 

But while medical intervention is largely successful in preventing the disease from becoming fatal, there is still significant risk, and necessary care can be costly. There are measured correlations between poverty and dengue fatalities. With over a quarter of Brazil’s citizens living below the poverty line, there is no doubt that the country’s dengue crisis is a serious threat. 

The nature of the virus lends itself to weather-dependence. Because it is mosquito-borne, there is a direct correlation between warmer, wetter weather and the prevalence of dengue. Considering that 2023 was the warmest year for South America in recorded history, it is no surprise that dengue has spiked out of control. Temperatures are expected to continue rising, and the year 2024 is already shaping up to be another one of the hottest on record. 

Photo Credit: The World Bank Group

In addition to the El Niño climate event—a cyclical “warm phase” of global climate patterns—there is little doubt that human activity is also to blame for the health crisis. Climate change has drastically affected South America—as well as the rest of the world—in recent years. Nine of the ten hottest years on record have occurred since 2012, and extreme weather events, such as wildfires and hurricanes, have become drastically more prevalent during that period. Brazil in particular is at risk primarily due to the changing Amazon rainforest. Deforestation and wildfires have interrupted the country’s ecosystem and prevented desperately needed CO2 absorption. Additionally, Brazil itself is one of the largest greenhouse gas emitters in the world. The Brazilian government joined the Paris Agreement in 2016, but progress has been slow. Even as the country fights to restore the Amazon and reduce greenhouse gas emissions, the years are growing steadily hotter, and health risks are increasing.  

In the face of rising temperatures, studies dating back to early 2023 predicted increased epidemic potential and longer transmission seasons for dengue. As temperatures continue to increase, dengue may become more and more common in all parts of the world, especially in South America. The University of Michigan School of Public Health predicts that dengue transmission could increase by as much as 20% by the year 2050. This has dangerous implications for the entire globe, and ought to be a wake-up call to the deadly effects of climate change. 

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This article was edited by Brianna Budhram and Natasha Tretter.