DENV-2 Dominants Peru's Dengue Outbreaks

Since 1980, the Pan American Health Organization has been collecting epidemiological data on the incidence of dengue. Following significant dengue fever outbreaks in South America during 2024 and 2025, researchers are investigating the root cause. 

For example, Peru has experienced severe national dengue outbreaks.

In 2010 and 2011, the Loreto region of Peru experienced an unprecedented dengue outbreak. In 2025, Peru reported over 270,000 cases and 261 deaths, which set records without a known clinical explanation.

A retrospective study (Volume 19, Issue 1) published by ScienceDirect in January 2026 offers new insights into the circulation patterns of dengue virus (DENV) serotypes in the Amazonas region of northeastern Peru from 2021 to 2025.

The research identifies DENV-2 as the dominant serotype driving major outbreaks in this Amazonian area while also revealing unexpected protective effects from prior infections against severe disease manifestations.

Furthermore, DENV-1 and DENV-3 circulated less frequently during the study period.

No direct association was found between specific serotypes and clinical classification, severity, or overall incidence rates.

Notably, prior dengue infection was significantly associated with a reduced likelihood of developing warning signs of severe dengue (p = 0.032), suggesting partial cross-protection during secondary infections.

"These results emphasize the critical role of DENV-2 in driving major dengue surges in Amazonas, while also highlighting how previous exposure to the virus may offer some protection against more severe symptoms," noted the lead researchers.

"This underscores the importance of sustained molecular surveillance to track DENV serotype shifts and inform targeted public health responses."

The findings from the Amazonas region align with broader trends in the Americas, where infection with one serotype does not confer complete immunity to others, and secondary infections can sometimes lead to severe forms of the disease.

This is essential information, as millions of international travelers visit Peru, many of whom visit Machu Picchu. 

Regarding which dengue vaccine offers the broadest protection, only one provides equivalent tetravalent protection against all four dengue virus serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). However, the single-dose Butantan-DV vaccine is only available in Brazil.

According to a 2025 survey, most people in Peru are interested in access to a next-generation dengue vaccine.