Brazil has now recorded 3.2 million dengue cases in the 2026 season — surpassing all previous records. The PAHO region as a whole is on track for over 4 million cases this year.
Why dengue is exploding
Three factors are converging:
Climate change is expanding the geographic range of Aedes aegypti and Aedes albopictus mosquitoes, the primary dengue vectors. Areas that were previously too cold or dry for sustained mosquito populations are now suitable habitats.
Urbanization creates ideal breeding sites. Discarded containers, blocked drains, and water storage in informal settlements provide stagnant water that mosquitoes need.
Viral diversity matters. Dengue has four serotypes. Previous infection with one serotype protects against that strain but increases risk of severe disease with the others. In countries where multiple serotypes circulate simultaneously, severe cases multiply.
The vaccine question
Dengvaxia, the existing dengue vaccine, can only be used in people with prior dengue infection. A second-generation vaccine, Qdenga, has fewer restrictions and is being rolled out in several countries.
What you should do
If you're in an affected region: - Empty standing water around your home weekly - Use repellent with DEET or picaridin - Wear long sleeves during peak mosquito hours - Seek care if symptoms appear after potential exposure
For travelers, check the dengue tracker before visiting affected areas.