Epidemiological shift in age distribution of dengue in Thailand, 2005–2024
- 1Khon Kaen University, Khon Kaen, Thailand
- 2Khon Kaen Provincial Public Health Office, Khon Kaen, Thailand
- 3Suratthani Rajabhat University, Surat Thani, Thailand
Abstract
Dengue has historically been characterized as a childhood disease, but evidence of shifting age distribution is increasing. We analyzed 20 years (2005–2024) of national dengue surveillance data from Thailand comprising 1,639,442 cases to examine temporal trends in age-specific incidence, quantify age shift magnitude using the ratio of incidence rate ratios (RIRR), and decompose observed changes using Kitagawa decomposition. The proportion of cases among adults ≥25 years nearly doubled from 19.56% to 36.16%, while the children’s proportion declined from 54.49% to 41.63%. RIRR for adults 25–44 years was 1.78 (95% CI 1.76-1.80), and for older adults ≥45 years was 2.19 (95% CI 2.15-2.24). Kitagawa decomposition attributed +178.7% of change to epidemiological factors and -78.7% to demographic shifts, supporting a declining force of infection rather than population aging as the primary driver. These findings necessitate expanding dengue prevention beyond school-based programs and enhancing clinical vigilance for adult dengue. Author summary: Dengue has long been regarded as a childhood disease, and prevention in endemic countries such as Thailand has centered on schools. Using two decades of national surveillance data (2005–2024) covering more than 1.6 million dengue cases, we show that the age of people affected by dengue in Thailand has shifted substantially upward. The average age of cases rose from about 17 to 26 years, and the share of cases in adults aged 25 years and older nearly doubled, from roughly one-fifth to more than one-third. This upward shift was seen in almost every province and region and, using a demographic decomposition method, was driven mainly by changing infection risk at each age (a declining “force of infection”) rather than by aging of the population itself. These findings indicate that dengue prevention, clinical vigilance and vaccination planning in Thailand and similar settings must expand beyond children to protect the growing number of affected adults, while continuing to safeguard children, who still bear the largest share of cases.
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BibTeX
@article{sornlorm2026epidemiological,
title = {{Epidemiological shift in age distribution of dengue in Thailand, 2005–2024}},
author = {Kittipong Sornlorm and Roshan Kumar Mahato and Sarayu Muntaphan and Kanit Hnuploy and Rajitra Nawawonganun},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = aug,
doi = {10.1371/journal.pntd.0014697},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014697},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Epidemiological shift in age distribution of dengue in Thailand, 2005–2024
AU - Kittipong Sornlorm
AU - Roshan Kumar Mahato
AU - Sarayu Muntaphan
AU - Kanit Hnuploy
AU - Rajitra Nawawonganun
PY - 2026
DA - 2026/08/31
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014697
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014697
AB - Dengue has historically been characterized as a childhood disease, but evidence of shifting age distribution is increasing. We analyzed 20 years (2005–2024) of national dengue surveillance data from Thailand comprising 1,639,442 cases to examine temporal trends in age-specific incidence, quantify age shift magnitude using the ratio of incidence rate ratios (RIRR), and decompose observed changes using Kitagawa decomposition. The proportion of cases among adults ≥25 years nearly doubled from 19.56% to 36.16%, while the children’s proportion declined from 54.49% to 41.63%. RIRR for adults 25–44 years was 1.78 (95% CI 1.76-1.80), and for older adults ≥45 years was 2.19 (95% CI 2.15-2.24). Kitagawa decomposition attributed +178.7% of change to epidemiological factors and -78.7% to demographic shifts, supporting a declining force of infection rather than population aging as the primary driver. These findings necessitate expanding dengue prevention beyond school-based programs and enhancing clinical vigilance for adult dengue. Author summary: Dengue has long been regarded as a childhood disease, and prevention in endemic countries such as Thailand has centered on schools. Using two decades of national surveillance data (2005–2024) covering more than 1.6 million dengue cases, we show that the age of people affected by dengue in Thailand has shifted substantially upward. The average age of cases rose from about 17 to 26 years, and the share of cases in adults aged 25 years and older nearly doubled, from roughly one-fifth to more than one-third. This upward shift was seen in almost every province and region and, using a demographic decomposition method, was driven mainly by changing infection risk at each age (a declining “force of infection”) rather than by aging of the population itself. These findings indicate that dengue prevention, clinical vigilance and vaccination planning in Thailand and similar settings must expand beyond children to protect the growing number of affected adults, while continuing to safeguard children, who still bear the largest share of cases.
SN - 1935-2735
ER -