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Dengue Virus: A Common Mosquito-Borne Threat in Latin America
Dengue, commonly known as breakbone fever, is the most widespread mosquito-borne disease worldwide, with Latin America being a major hotspot. It is a viral disease caused by the dengue virus (DENV), which belongs to the Flaviviridae family. Interestingly, the term Flaviviridae comes from the Latin word flavus (meaning yellow), referencing the yellow fever virus, another virus from the same family.
Flaviviridae viruses, like dengue virus, are incredibly special. They are a type of virus named an arbovirus (arthropod-borne virus), which is transferred to humans through the help of vector, namely that which everyone loves: the mosquito (a type of arthropod).
The primary mosquito transmitting dengue is the Aedes aegypti vector (Figure 1), becoming infected when it bites an already infected person. Once infected, the mosquito spreads the virus to humans through subsequent bites.
Mosquitoes thrive in tropical and subtropical climates favoring warm temperatures (~80°F / 27°C), high humidity levels, and stagnant water sources (perfect breeding grounds). Due to these conditions, Latin America reports a significant percentage of global dengue cases every year.
Dengue in 2024: A Record-Breaking Outbreak
In 2024, the Pan American Health Organization (PAHO) issued a critical warning about the rapid spread of dengue in Latin America and the Caribbean with 12.6 million+ dengue cases and 1,000+ deaths.
The worst-hit countries included Brazil, Argentina, Colombia, and Mexico. According to Statista, this is the highest number of dengue infections recorded in the region between 2016 and 2024 (Figure 1).
In this blog, I explore four key reasons: mosquito species, lack of vaccines and antivirals, climate change, and mortality predictors and risk factors.
Figure 1. Aedes aegypti cases in Latin America from 2021-2024. Aedes aegypti means “of Egypt” in Latin since the mosquito originates in Africa. Data obtained from Statista.
Why Are Dengue Cases Skyrocketing in Latin America?
1. Spread of Mosquito Species
A 2022 review by Egit et al. found that the rising urbanization, climate change, and international travel have contributed to the spread of these mosquitoes into previously dengue-free areas (WHO). Latin America is home to two primary dengue-carrying mosquito species(Figure 2):
- Aedes aegypti (Ae. aegypti): The primary vector, commonly found in urban and peri-urban environments. It prefers to stay indoors, near people, and thrives in cities. Ae. aegypti is endophagic (feeds indoors) and endophilic.
- Aedes albopictus (Ae. albopictus): Found outdoors, in rural and semi-urban areas. Ae. albopictus is exophagic (feeds outdoors) and exophilic (prefers open spaces).
Figure 2. Key factors driving increasing dengue vector spread.
2. Virus Evolution and Mutation
The dengue virus (DENV) has evolved significantly over time. Initially believed to have originated in nonhuman primates, it later jumped to humans in Africa or Southeast Asia around 500-1,000 years ago.
The virus has now evolved into four distinct serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. Serotypes refer to isolated dengue viruses that interact differently with our antibodies, protein components of the immune system travelling through the human blood. Each serotype interacts differently with human antibodies, which complicates immunity and vaccination efforts.
One major concern with dengue is antibody-dependent enhancement (ADE), a phenomenon where:
- A person infected with one serotype of dengue develops immunity against it.
- However, if later infected with a different serotype, their existing antibodies worsen the infection rather than protecting them.
Studies show that dengue has a high mutation rate (7.5×10-4mutations/position/year), which is higher than other RNA viruses but still slower than the HIV and the never-ending influenza viruses.
The paper by Dolan et al. investigated certain factors increasing dengue virus evolvability. They found dengue acquires beneficial mutations that preferentially map to certain regions within the viral proteins and cluster in specific defined regions in the viral genome. This redundant adaptiveness may facilitate host-specific dengue virus adaptation.
Another paper by Katzelnick et al. published in the journal Science also discovered that our body’s immune response to the virus is a source of evolutionary pressure and shapes viral antigenic variation.
Antigenic variation occurs when the dengue virus tries to evade the immune system and alters the surface proteins or carbohydrates (antigens) of the proteins that recognize the virus parts. This then decreases the activation and efficiency of our immune system against the dengue virus.
3. Lack of Effective Vaccines and Antivirals
One of the biggest challenges in dengue prevention is the lack of a effective universal vaccines for all four dengue virus serotypes (Figure 3). Currently there are two licensed live-attenuated vaccines, CYD-TDV (Dengvaxia®) and Qdenga, that do not yield long-lasting, balanced immune protection against all serotypes and are only available in a few countries. Brazil, Merica, and Thailand have use them in vaccination program initiatives.
Developing treatments has been difficult mainly because of two reasons:
- Dengue virus replicates poorly in current animal models, making it hard to test vaccines and drugs.
- Traditional animal models like mice and monkeys do not accurately mimic human dengue infections.
Choosing an animal model for dengue virus studies requires meeting specific criteria, including signs of dengue viraemia, susceptibility, immune function, clinical symptoms, antibody-dependent enhancement, and cytokine storm response (inflammation).
As reviewed by Yuya et al. models include non-human primates, immunocompromised and humanized mice, swine, and tree shrews. However, limitations persist due to low replication levels and unreliable mimicry of disease.
Figure 3. Factors influencing prevalence of dengue virus in Latin America.
4. Climate Change: A Key Factor in Dengue Spread
Climate change is drastically altering mosquito habitats, expanding dengue transmission to higher latitudes and altitudes. As of March 2024, Brazil, Paraguay, and Argentina reported massive dengue outbreaks due to unusually warm and rainy conditions.
Key Climate Factors Driving Dengue Transmission:
- Rising Temperatures. Warmer climates accelerate mosquito lifecycles, increasing their biting rates and ability to spread the virus. Higher temperatures also extend mosquito activity, leading to longer transmission seasons.
- Increased Rainfall. More rain creates stagnant water pools, perfect breeding grounds for mosquitoes.
- High Humidity. Higher humidity was found to be significantly associated with the prevalence of dengue fever in the study done by Monintja et al, where the authors analyze the association between temperature and humidity and dengue fever incidence in Manado Municipality. Higher humidity is also associated with increased Aedes aegypti feeding activity, survival, and egg development.
5. Mortality Predictors and Risk Factors
Understanding dengue mortality risk factors is crucial for improving public health strategies, particularly in regions with high infection rates like Mexico, the Caribbean, and Latin America.
A study performed by Fonseca-Portilla et al. on dengue-related hospitalization and mortality in Mexico found that children under 10 and adults over 60 face a higher risk of severe complications. Additionally, underlying health conditions such as diabetes, hypertension, pregnancy, immunosuppression, and chronic kidney disease significantly increase the likelihood of hospitalization and death due to severe dengue fever.
In an observational ecological study, Diaz-Quijano and Waldman analyzed data from 1995 to 2009, revealing that dengue mortality rates were highest in the Caribbean. Their findings indicate that annual rainfall, population density, human development index (HDI), and the prevalence of Dengue-2 serotype have contributed to increasing dengue severity in Latin America.
Further evidence from a systematic review by Paraná et al. (which analyzed 1,876 studies) highlights that secondary dengue infection and female sex are additional risk factors for severe dengue complications. Given the rising dengue mortality rates in Latin America and the Caribbean, proactive vector control measures, early detection, and improved healthcare access are essential to reducing the disease’s impact.
Final Thoughts
Dengue is no longer just a seasonal tropical disease—it’s a growing global health crisis.
Preventive measures, mosquito control, and vaccination programs, especially in Latin America, must be scaled up to combat the rise in cases. Further research into virus evolution and climate-driven outbreaks is crucial for developing better treatments.
