Dengue cases soared to record highs in the Americas region during 2024

Dengue cases in the Americas skyrocketed to over 11 million by August of 2024, more than doubling the 4.6 million cases reported during the whole of 2023.^1,2 This unprecedented surge prompted Pan American Health Organization (PAHO) Director Jarbas Barbosa to declare that "an emergency situation" had been reached.^2,3

Record-breaking: Dengue cases in the Americas during the first half of 2024 were substantially higher than anything seen years before^2,4

Total number of reported dengue cases in the Americas region: 2000 – 2024. Adapted from: Pan American Health Organization (PAHO)⁴

A regional crisis

Let’s take a closer look at this outbreak and the implications it may hold for the future of dengue – in terms of its incidence and management – in the Americas region and beyond.

Where

• Across the Americas region, Brazil has been the most affected country, followed by Argentina, Peru, Columbia and Paraguay⁵

The numbers

• Reported suspected cases for the most affected nations were: Brazil (6,520,234),⁶ Argentina (764,901),⁷ Peru (259,454),⁸ Columbia (243,146)⁹ and Paraguay (227,845)¹⁰ 

• During the first half of 2024, all countries in Latin America and the Caribbean recorded increases in cases compared to the same period in 2023¹¹

• Six countries (Brazil, Costa Rica, Guatemala, Honduras, Mexico, and Panama) already reported the simultaneous circulation of all four dengue virus serotypes¹²

The impact

• Multiple countries, including Peru, Puerto Rico, Honduras and certain states of Brazil, declared public health emergencies^2,13-17

• Authorities in Peru had to set up emergency tents on sports pitches to accommodate the sheer number of patients¹⁶

• Army troops were deployed in Brazil’s capital to help track the breeding spots of dengue-carrying mosquitoes¹⁷

Argentina experienced an insect repellent shortage with some people resorting to “home-made” repellants.^18,19 There were also increased patient waiting times of up to 11 hours in some parts of the country²⁰

The contributing causes

• The expansion of the dengue-carrying Aedes aegypti mosquito to new areas, possibly due to factors such as El Niño and climate change¹¹

• Rapid unplanned urban expansion and population growth, combined with poor water and sanitation services in many places created favorable conditions for the proliferation of mosquitoes in discarded objects and containers that accumulate water¹¹

• Limited contact between humans and the dengue virus because of isolation measures and travel restrictions during the COVID-19 pandemic may have increased the number of people susceptible to dengue.¹¹ Following this, the lifting of the restrictions and rebound travel post-Covid may have then helped the virus spread¹⁶

The response

On a regional level

• PAHO issued an epidemiological alert which emphasized the importance of strengthening surveillance, diagnosis and vector control actions, as well as preparing health services for the proper management of patient²¹

• PAHO stated that the overall aim was to prevent complications and avoid possible overcrowding of health services²¹

• Other guidance issued by PAHO and World Health Organization (WHO) to its member states called for the use of multiple interventions, often in combination and “synergistically”²²

• The guidance emphasized the role of the community in dengue prevention and control efforts:²²

On a national level

• In Peru, the government of President Dina Boluarte approved an emergency order that allowed for “extraordinary economic measures”, releasing funds to counter the outbreak²³

• In the United States, the CDC issued a Health Alert Network (HAN) Health Advisory to notify and advise healthcare providers, public health authorities and the public of an increased risk of dengue infections in the US²

• In Argentina, government authorities lifted import restrictions of mosquito spray to help meet demand²⁴

• While Brazil had begun a dengue vaccination program in 2024, the country has struggled with supply issues and low uptake.^3,25

Dr. Jarbas Barbosa, PAHO/WHO Director, highlighted that while dengue vaccines have the potential to significantly reduce severe cases and fatalities in Brazil, it may take some time before their impact is seen in a reduction of overall dengue cases.²⁵

Looking ahead: Will dengue continue to set record highs in the Americas?

• Climate change, urbanization, and global travel have been implicated as main reasons for the global increase of dengue.² As these factors show no signs of abating in the future, they may therefore fuel future rises in dengue cases – and potentially expand its reach to new regions

• Another concern is that in future years, individuals infected during this outbreak could be reinfected with a different serotype. A secondary infection with a different serotype increases the risk of severe dengue, a more serious form of disease^27,28

A call to action

• The 2024 dengue outbreak in the Americas highlights the urgent need for coordinated and collaborative efforts which involve improved surveillance, vector control measures and public health interventions to prevent future – possibly even bigger – outbreaks

• Countries are taking steps in the right direction and seeing positive results. Despite the unprecedented number of dengue cases during this outbreak, the fatality rate (of 0.048%, in the first half of 2024) remained below the regional goal of 0.05%¹¹

The 2024 dengue outbreak can be seen as a wake-up call, underscoring the need for coordinated efforts in surveillance, vector control, and public health interventions. While the fatality rate remained low,¹¹ the immense strain placed by the outbreak on healthcare systems^16,20 – along with the national emergencies it triggered across multiple countries^2,13-17 – highlights the importance of sustained vigilance to prevent even larger crises in the future.