Cycles on dengue incidence and mortality: Evaluating data from the global burden of diseases

Introduction

Dengue is a neglected disease caused by a virus from the Flavivirus genus and primarily transmitted by Aedes aegypti mosquitoes.¹ Clinically, it presents as an acute febrile condition, marked by high fever, severe headaches, muscle and joint pains, nausea, vomiting, and skin rash.² In some cases, the disease can progress to severe forms, marked by warning signs such as intense abdominal pain, persistent vomiting, and bleeding, which may be fatal if not corrected managed.²

Globally, dengue imposes an increasing burden on global health. In fact, its case burden increased from ∼23.3 million in 1990 to 62.1 million in 2021, while dengue-related deaths rose from 14,300 to >32,500 in the same period.^3–5 Only in 2024, >12.4 million cases were officially reported, almost doubling cases in 2023.^3,4

Focusing on specific regions, dengue's burden remains notable. ⁴ In the Americas, a historic record of 12.6 million suspected cases and over 7700 deaths were reported only in 2024, and from 1990 to 2021, the annual number of cases in the region more than doubled.⁵ In the Western Pacific Region, some countries such as Vietnam and Cambodia, reported more than 650,000 dengue cases in 2023.^3,5 In Africa, dengue has emerged as a growing concern, with outbreaks in countries including Burkina Faso and Kenya, with over 50,000 cases registered in 2023.^4,5

Cyclical periodicity could enhance surveillance, resource allocation, and intervention planning, reducing dengue's incidence and mortality. ⁶ Thus, this study aimed to evaluate the cyclicity in dengue's incidence and mortality.

Methods

Our ecological study evaluated the cyclicity in the incidence and mortality of dengue between 1980 and 2021. All data were provided by the global burden of disease (GBD). This is a comprehensive research initiative that evaluates health loss by diseases, injuries, and risk factors worldwide. It was conducted by the Institute for Health Metrics and Evaluation and employs data from multiple sources, aiming to estimate the prevalence, incidence, mortality, and other variables.

Data collection was carried out manually by the author by transposing the collected data into Google spreadsheets. After that, data were stratified by their World Bank region (whole world, North America, Latin America and the Caribbean, sub-Saharan Africa, North Africa and the Middle East, Europe and Central Asia, South Asia, as well as East Asia and the Pacific), reported year, and dengue's incidence (1990–2021) and mortality (1980–2021) by 100,000 individuals for each region and year.

Using the R software 4.4.2, periodic patterns in the time series data were identified by applying a Hanning window function, a fast Fourier transform algorithm, a locally estimated scatterplot smoothing filter, a harmonic regression, and a power spectral density. This, the chosen analytical method transforms a time series into sinusoidal segments capable of being transcribed in trigonometric functions, in which it is possible to observe a cycle and determine which is the best model to fit in according with data behaviour.

Possible cycles range from 0 years (absence of cycles) to 31/41 years (one complete cycle within the time frame), with increments of 0.1 years to ensure precise identification of periodic patterns. Each cycle was evaluated by the statistical significance of its sine and cosine terms, its 95% confidence interval, range, and its fit on the data display.

Results

Regarding the mortality in cycles, South Asia exhibited cycles of 28.5 years, which started around 1980 and finished in 2008, and is expected to produce another cycle between 2008 and 2036. East Asia and the Pacific present cycles of 29 years, which range between 1980 and 2009 and are expected to continue between 2009 and 2036. Latin America and the Caribbean presented cycles of 27.2 years occurring between 1980 and 2007, also expected to recur between 2007 and 2034. Finally, a global cyclicity of 30.1 years was observed between 1980 and 2010 and is expected to recur between 2010 and 2040. Other evaluated regions did not show statistically significant cycles (Fig. 1).

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Figure 1.

Cyclical variations in dengue mortality rates between 1980 and 2021 by world regions.

Regarding the incidence, sub-Saharan Africa exhibited cycles of 24.2 years, which started approximately around 1990 and finished in 2014, which are expected to repeat between 2014 and 2038. South Asia presented cycles of 21.1 years, occurring between 1990 and 2011, expected to recur between 2011 and 2032. The Middle East and North Africa showed cycles of 21.8 years, ranging from 1990 to 2012, with a subsequent cycle estimated to span between 2012 and 2034. Latin America and the Caribbean presented shorter cycles of 16.9 years, observed between 1990 and 2007, and anticipated to repeat between 2007 and 2024. Globally, a periodicity of 19.8 years was detected, with cycles observed between 1990 and 2010 and expected between 2010 and 2030. East Asia and the Pacific exhibited longer cycles of 30.6 years, ranging between 1990 and 2020, and predicted to extend from 2020 to 2050. Finally, North America showed cycles of 25.7 years, occurring approximately between 1990 and 2016, with a new cycle projected between 2016 and 2042 (Fig. 2).

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Figure 2.

Cyclical variations in dengue incidence rates between 1980 and 2021 by world regions.

A more detailed perspective of the obtained results can be observed in the Supplemental tables.

Discussion

Our study identified cyclical patterns which probably reflect a profound interplay between climatic and environmental conditions.^7–9 Indeed, in tropical and subtropical areas – particularly Latin America, sub-Saharan Africa, and Southeast Asia – recurring patterns of rainfall, humidity, and temperature peaks provide optimal conditions for Aedes mosquito proliferation.^7,8

Furthermore, monsoon seasons and climate oscillations such as El Niño and La Niña periodically exacerbate the natural conditions of these regions, amplifying vector densities and viral transmission, which may explain the waves of incidence approximately every two to three decades. ⁹

In contrast, temperate and subtropical regions such as North America exhibit longer cycles, possibly due to the occurrence of episodic warming events that now appear in these locations.^10,11 Not less important, it should be mentioned that global warming seems to be changing this pattern.^10,11 Thus, a higher dengue vector proliferation is on course, producing an increase in dengue infections and, consequently, in deaths.^10,11

Further, urbanisation and socio-economic disparities also contribute to the observed cyclical trends. ¹² These have created dense settlements with inadequate water management, sanitation, and waste disposal, establishing persistent breeding sites for dengue vectors.^12,13 Consequently, the recurrence of cycles in Latin America and South Asia may be linked to waves of infrastructural expansion, migration, which periodically amplify this scenario. ¹⁴ Additionally, economic crises and political instabilities often reduce funding for public health programmes, enabling the resurgence of epidemics after transient control successes, thus determining a new observed cyclicity. ¹⁵

Furthermore, biological factors, including the circulation of multiple dengue serotypes and the introduction of new or hypervirulent strains, also probably underpin the cyclical nature of outbreaks. ¹⁶ Under this perspective, in regions such as Latin America and sub-Saharan Africa, periodic emergence of new serotypes and resurgence of other ones has been associated with increased dengue severity and mortality, particularly when populations previously exposed to other serotypes experienced antibody-dependent enhancement.^16,17 Also, the overlap with endemic diseases such as Chikungunya and yellow fever compounds these cycles not only by sharing common vectors, but also by straining health systems and increasing the likelihood of severe outcomes. ¹⁷

Interestingly, while East Asia and the Pacific display long cycles similar to the global periodicity, regions such as the Middle East and North Africa exhibited shorter, more fragmented cycles. ¹⁸ These divergent patterns may reflect the differential effectiveness of control policies, the impact of armed conflicts disrupting health infrastructure, and varying baseline immunity. ¹⁹ Comparing regions with sustained low mortality cycles, such as North America, to those with pronounced oscillations, it may be possible to hypothesise how critical is the role of continuous investment in vector control and healthcare capacity. ²⁰

Understanding the predictability of dengue's cyclical patterns offers a unique opportunity to anticipate and mitigate future dengue epidemics.^21,22 Thus, health authorities can integrate cycle projections into surveillance planning, scaling up entomological monitoring and early warning systems in advance of expected peaks, thus mitigating their occurrence. ²³ Strategic stockpiling of diagnostic supplies and vector control materials should be aligned with projected cycles to avoid reactive shortages during surges, granting individuals access to health care and providing them with a prompt diagnosis and enough treatment. ²⁴

At the policy level, long-term investment in resilient infrastructure – such as improved drainage, housing, and waste management – can disrupt the environmental conditions that sustain cyclical transmission. ²⁵ Moreover, community engagement campaigns timed to precede anticipated outbreaks may enhance awareness and reinforce behaviour that reduces breeding sites. ²⁶ Additionally, fostering international cooperation to share data on climatic trends, serotype shifts, and intervention effectiveness can refine predictive models, supporting more proactive, evidence-based responses across regions. ²⁶

Our study, therefore, provides a novel and comprehensive analysis of the periodicity in dengue incidence and mortality over three/four decades using robust statistical methods. It provides valuable insights into dengue epidemiology and informs public health strategies. However, there are some limitations. First, as an ecological study, it does not account for individual-level risk factors that may influence dengue trends. Second, while the GBD dataset is comprehensive, it relies on modelled estimates that may be subject to reporting biases and data gaps, particularly in low-resource settings.

Conclusion

The observed differences in dengue incidence and mortality cycles across regions highlight the multifaceted nature of the disease, influenced by climate, healthcare infrastructure, economic stability, and sociopolitical factors. Regions with robust vector control and healthcare systems, such as North America and Europe, exhibit longer incidence cycles and lower mortality rates. In contrast, regions with high endemicity, such as Latin America and South Asia, experience shorter, more frequent cycles. Political instability, natural disasters, and insufficient healthcare access exacerbate these disparities, necessitating tailored intervention strategies for effective dengue management.

Supplemental Material