Officials declare emergency amid surge in deaths from disease carried by mosquitoes — here's what you need to know

The Brazilian state of São Paulo recently declared a public health emergency amid a rise in dengue-related deaths.

What's happening?

The alert was sent out by its health department in February, and by May 26, it had reported around 617,000 of Brazil's 2.5 million dengue cases for the year, according to Vax Before Travel, which reported on the developing public health dilemma. São Paulo also led the country in dengue-related deaths, with 692, the publication added, citing government data.

This is nothing new for São Paulo — according to Vax Before Travel, the state reported about 2.1 million dengue cases and 2,100 related fatalities in 2024.

Why is the dengue outbreak concerning?

Dengue fever is a vector-borne disease that is carried by mosquitoes. According to the Mayo Clinic, it can cause symptoms like high fever, headache, muscle, bone or joint pain, nausea, vomiting, pain behind the eyes, swollen glands, and rash.

The World Mosquito Program called 2024 the "worst year for dengue cases on record, and many experts believe that this spike was in part driven by rising global temperatures. In fact, a number of studies have indicated that warmer temperatures are helping mosquitoes increase their populations and expand their ranges, which can expedite the spread of vector-borne diseases like dengue, malaria, Zika, and West Nile virus. 

For instance, one recent study found that several mosquito species could expand across the Americas because of warmer temperatures. San Diego County in 2024 reported its first-ever locally acquired case of dengue. 

What's being done about vector-borne diseases?

When officials in San Diego County learned that dengue had arrived there, they quickly sprayed neighborhoods for mosquitoes. Meanwhile, officials in one Florida county are using X-rays to kill invasive mosquitoes there.

You can decrease your risk of diseases carried by mosquitoes by taking steps to avoid getting bitten. The Centers for Disease Control and Prevention recommends using Environmental Protection Agency-registered insect repellents, wearing loose-fitting, long clothing, and treating clothing and gear with 0.5% permethrin. 

Vax Before Travel also reported that while a second-generation dengue vaccine will be limited in availability in 2025, São Paulo's Butantan Institute is helping to develop a vaccine that could become available in 2026.

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