In 2025, the Region of the Americas has seen a significant decrease in Dengue Fever cases, especially in the Republic of Costa Rica.
This popular Central American vacation destination has reported over 3,900 cases of Dengue this year, which poses a considerable health risk to international travelers.
However, data from the Costa Rica Health Department’s Boletín Epidemiológico No. 36 reveal a significant reversal of the outbreak this year, compared to 31,259 cases in 2024 and 30,649 in 2023.
In Costa Rica, Dengue transmission has become increasingly complex, with the co-circulation of all four DENV serotypes (DENV1–4), increasing the risk of co-infections.
Historically, DENV1 and DENV2 predominated, but DENV4 emerged in late 2022, followed by the reappearance of DENV3 in early 2023.
The highest incidence rates of this mosquito-transmitted disease have been reported in San José, Alajuela, and Puntarenas.
Published in May 2025, this preprint study offers the first nationwide genomic and eco-epidemiological assessment of Dengue in Costa Rica, highlighting the recent replacement of DENV2-III (Asian-American) by the emerging DENV2-II (Cosmopolitan) genotype.
These researchers demonstrated how viral evolution and ecological factors shape transmission. Similar genotype replacements have occurred elsewhere, often associated with shifts in immunity or viral fitness advantages.
However, they found no evidence of increased transmission due to climate or age-related shifts in infection.
These researchers wrote, While our genomic data are substantial, uneven geographic sampling and reliance on passive surveillance limited detection in some areas. Overall, this study highlights how the interactions between genotype introductions, ecological conditions, and human mobility shape dengue transmission dynamics in Costa Rica.
Strengthening real-time genomic surveillance systems integrated with environmental and mobility data is essential for early detection of emerging threats and for guiding timely, targeted public health interventions.
This advice is applicable in the United States, as the U.S. CDC has cautioned providers to evaluate international travelers returning from areas with arbovirus disease outbreaks more closely.
As of September 29, 2025, Dengue vaccines are generally unavailable in the United States, except for children in Puerto Rico.
Globally, a second-generation Dengue vaccine is offered in many countries, but it does not protect against all four Dengue virus types.
According to various news articles, next-generation Dengue vaccine candidates are making progress in clinical trials, but are unlikely to become available in 2026.