Dengue Risk Increases in the Americas as DENV-3 Circulates

The Pan American Health Organization (PAHO) has issued an epidemiological alert regarding the increased risk of dengue outbreaks across the Americas. This alert follows the growing circulation of the DENV-3 serotype in several countries within the region. PAHO has advised countries to strengthen their surveillance, early diagnosis, and medical care efforts in anticipation of potential rises in dengue cases.

Dengue is a viral disease transmitted by the Aedes aegypti mosquito and is characterized by four serotypes including DENV-1, DENV-2, DENV-3, and DENV-4, reports PAHO. Immunity to one serotype provides long-term protection only against that specific type, meaning subsequent infections by other serotypes can increase the risk of severe disease. The emergence or increased presence of a serotype that was not previously dominant in a region can lead to a rise in cases, as populations may be more susceptible.

The DENV-3 serotype has been detected in various countries, including Brazil, Colombia, Costa Rica, Guatemala, Mexico, and Peru. Argentina reported its circulation for the first time in 2024. Both Brazil and Colombia experienced a significant uptick in cases linked to DENV-3 in 2024, especially among children. The serotype has also been found in other parts of Central America and the Caribbean. DENV-3 is associated with severe forms of the disease, even in primary infections, heightening concerns about its potential impact on public health. The reappearance of DENV-3, after a long absence in some regions, increases the vulnerability of populations that have not been exposed to it before.

In 2024, over 13 million cases of dengue were reported across the Americas, with 22,684 classified as severe and 8,186 resulting in deaths, yielding a fatality rate of 0.063%. In the early weeks of 2025, 23 countries and territories reported 238,659 cases, with the majority concentrated in Brazil, followed by Colombia, Nicaragua, Peru, and Mexico. Of these cases, 263 were severe, and 23 deaths were recorded.

The TAK-003 dengue vaccine, which is used in some countries in the region, has shown lower effectiveness against DENV-3, particularly in children without prior infection. PAHO continues to monitor the evolution of DENV-3 and other serotypes and will provide support to countries in implementing effective control and response measures in the event of potential outbreaks.