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Jun 6, 2024, 1:46pm EDT
South America
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Semafor Signals

Brazil is in the grip of a dengue fever outbreak with no end in sight

Insights from Medscape, The Washington Post, and Nature

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Sanofi Pasteur/Marizilda Cruppe/Reuters
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Brazil has registered a record-breaking 5.5 million cases of dengue fever this year, a mosquito-borne virus that causes high fevers, rashes, and in some cases, death.

The surge in dengue has been fuelled by high temperatures induced by both climate change and the El Niño weather pattern, scientists and medical experts say.

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Brazil is a case in point. Regions once relatively free of mosquitoes, such as North America and Europe, are becoming potential hotspots for the disease. In Paris, authorities have deployed “dengue detectives” to surveil mosquitoes ahead of the Olympic Games, and health officials last year warned the UK could become home to invasive mosquitoes by 2050.

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SIGNALS

Semafor Signals: Global insights on today's biggest stories.

Brazilians face a four-pronged dengue attack

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Sources:  
Medscape, The Washington Post, VaccinesWork

Four different strains of dengue are sweeping Brazil at the same time; the disease has been endemic to the country since the mid-1980s, but many people lack the immune defenses needed to fight the virus now, “probably keeping infection rates elevated,” medical experts argued in Medscape. The outbreak is particularly perilous, because people can catch dengue multiple times over a short period, an epidemiologist told the Washington Post: Infection doesn’t confer long-lasting immunity, and subsequent infections can prove more deadly due to a biological process called antibody-dependent enhancement, which enables the virus to replicate faster, according to VaccinesWork.



In Brazil, dengue is an urban disease

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Sources:  
The International Water Association, Nature , ThinkLandscape

Mosquitoes lay their eggs in standing water, and many Brazilians are forced to store water in open tanks due to long-term underinvestment in adequate water and sanitation infrastructure, particularly those living in informal urban settlements. “The cities are growing and becoming paradise for mosquitoes,” a professor of global health told science journal Nature. Dengue transmission in rural areas isn’t common, but people there are perhaps more vulnerable if they are infected, as health workers are less familiar with the disease, a researcher at Brazil’s Climate and Health Observatory told ThinkLandscape.

Vaccines aren’t a silver bullet

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Sources:  
The New York Times , Science , ThinkLandscape

Brazil bought the entire global stock of a Japanese-made dengue vaccine in January but the stilted roll out of its two-dose regimen means only 1.5% of the population will be vaccinated this year, the New York Times reported — not enough to achieve herd immunity and slow the virus’ spread. Various home-grown vaccine development projects are underway, but the fruit of that labor will not be available until 2025 at the earliest. “We are frenetically working against time,” the director of the Butantan Institute, which is developing a new vaccine, told academic journal Science. But vaccinations are no silver bullet against dengue: “It’s not like measles, where you give a vaccine and it’s end of story,” the head of Dengue Global Program and Scientific Affairs at the Drugs for Neglected Diseases Initiative told NPR. Instead, dengue requires a multi-prong approach, she said.

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