Dengue outbreak in Brazil: 2024

Brazil faced one of its worst-ever dengue outbreaks in 2024, with numbers of cases and deaths totalling over 6.5 million and 5,000, respectively (as of August 2024).^1,2 Prior to this outbreak, Brazil already had the highest number of dengue cases in the world in 2023, accounting for 2.9 million out of 5 million reported cases.³ Dengue cases in the Americas region as a whole too, in the first half of 2024, far exceeded those during the whole of 2023.⁴

Where

• The whole country was affected.² The Federal District was among the places with the highest rate of infections⁵

The numbers

• 6,500,034 dengue cases as of August 2024¹

The contributing causes

• A heat wave in conjunction with El Niño (a climate pattern) – rising temperatures and unusually heavy rains created conditions that favored dengue-carrying A.aegypti mosquitos.^6,7 This coincided with the simultaneous circulation of different serotypes of the dengue virus.⁴ One of the issues with this is that a person infected a second time with a different dengue virus serotype could be at a higher risk of developing severe dengue⁸

• Long-standing factors such as inequality and poverty further exacerbated the problem.⁹ A large proportion of Brazilians live in densely populated favelas or “the periphery” which government services and basic utilities do not extend to. As a result, residents could be left with unreliable plumbing, forcing them to store water outside – thereby creating additional breeding sites for mosquitoes⁹

The impact

• At least 17 cities, including Rio de Janeiro, declared a state of emergency¹⁰

• In cities across the country, hospitals and doctors were stretched to the limit.¹¹ There were reports of hospital beds running out and of patients being turned away in some regions⁹

• Brazil’s army helped build field hospitals in the capital, Brasília, to accommodate the overflow of patients from swamped emergency departments¹²

The response

• A national control center to coordinate efforts to protect the population was set up¹³

• Health officials urged people to apply insect repellent and to ensure that they checked their homes for any stagnant water/potential mosquito breeding sites⁶

• “Dengue-fighting” mosquitoes were released in some Brazilian cities. These mosquitoes are infected with Wolbachia bacteria which, while not harmful to the mosquito, inhibit the dengue virus^13,14

Looking ahead

• The importance of community action cannot be overstated in Brazil’s battle against dengue: dengue is more likely to occur in areas of inequality among populations with less access to information, lower incomes and exposure to sanitary insecurity. And so, SUS (Brazil’s health service) community agents are extremely important in conveying information directly to the homes of the most vulnerable people and in identifying places that need prevention measures¹³

• Brazil has launched a nationwide vaccination campaign, which, as part of an integrated approach (including efforts by public health experts such as locating potential mosquito breeding sites) aims to help combat dengue⁷

A new phase?

• Looking to the future, effective dengue control is needed now, more than ever before, as the mechanics behind dengue outbreaks may be entering a new phase:

• Indeed, some epidemiologists have speculated that the situation in Brazil may serve as a warning to the world, highlighting that: “The struggle against the disease has entered an unpredictable, perilous new phase. Dengue is creeping into places where it has never been. And where it has long been, case numbers are soaring to unseen heights”⁹