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Health officials to release millions of insects to fight outbreak of 'break-bone' fever — here's how they'll help

"Our projections show that within 10 years, we will be able to protect around 70 million Brazilians across various cities."

"Our projections show that within 10 years, we will be able to protect around 70 million Brazilians across various cities."

Photo Credit: iStock

Amid a severe outbreak of dengue fever in Brazil, a swarm of unlikely heroes was tabbed to be part of the solution.

What happened?

As explained in The Guardian, the country planned to release bacteria-infected mosquitoes to six Brazilian cities in hopes of fighting the outbreak. These mosquitoes were exposed to a bacteria called Wolbachia, which is not naturally present in the species of mosquitoes that carry dengue fever. 

The Wolbachia method was found to be effective after it was introduced to five Brazilian cities, as 3.2 million people were provided with protection. Bringing it to six new cities will further protect another 1.7 million.

The city of Niterói, which sits across Guanabara Bay from Rio de Janeiro and has around 500,000 inhabitants, was the first to get full Wolbachia coverage after being a part of the pilot project in 2015. The numbers stayed low even after Rio de Janeiro declared an emergency in February, as the Wolbachia method was rolled out on a smaller scale because of the challenges presented by Brazil's second-largest city.

"Rio is a city with 12 times the population but [nearly] 100 times more dengue cases than Niterói," said Axel Grael, the mayor of Niterói. "There is no doubt that the application of the Wolbachia strategy has been decisive for our results."

Why is this important?

Dengue fever can cause severe muscle spasms and joint pain, earning its "break-bone" nickname. Other symptoms include fever, nausea, vomiting, and rash, and the disease can lead to death. It is difficult to track because the majority of cases are asymptomatic or mild.

Health officials have warned that dengue fever is expected to become a major threat this decade. Rising global temperatures have allowed mosquitoes to expand their territory, causing the spread of vector-borne diseases including dengue, malaria and Zika.

At the time of the report by The Guardian, 1.6 million probable cases of dengue fever had been tracked since January, matching the total from the entirety of 2023. Dengue had led to 491 deaths, with an additional 889 cases remaining under investigation.

What's being done about this?

A Rio de Janeiro lab in a public health institute run by the health science organization Fiocruz will be providing eggs and larvae of Wolbachia-infected mosquitoes, nicknamed "wolbitos," to the cities. Fiocruz regulates the Wolbachia method in Brazil in conjunction with the World Mosquito Program and with support from the health ministry.

"We have a list of more than 50 municipalities that have got in touch requesting [wolbitos]," said Luciano Moreira, a Fiocruz researcher who leads the WMP in Brazil. "Our biggest bottleneck right now is the production of mosquitoes."

A new mosquito-breeding lab that should be ready to begin operation in 2025 will also help increase production.

"Our projections show that within 10 years, we will be able to protect around 70 million Brazilians across various cities," Moreira added.

In addition to the Wolbachia method, community health agents were deployed to the cities in hopes of finding and eliminating sources of stagnant water that foster breeding grounds for mosquitoes. The government has also rolled out vaccines to limit the transmission of dengue.

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