The fly that Brazil can’t swat

Every year it’s the same story. The Ministry of Health releases TV advertisements with advice on how to prevent the proliferation of Aedes aegypti, the mosquito that causes dengue fever and transmits the Zika virus. The pests like clean, standing water, which can easily accumulate in gardens, potted plants, and the like. Yet, every summer inevitably sees a rise in the number of dengue fever cases in the country’s warmest areas, such as Rio de Janeiro and the Northeast. This year, however, things have gotten even worse.

The number of probable cases of dengue fever in Brazil spiked in 2019—way before the usual season has begun—after two years of low levels of infections. Between January and August, authorities recorded 599 percent more cases than in the same period of last year, leading the government to bring forward its summertime anti-mosquito campaigns. 

In the first 34 weeks of 2019, over 1.4 million cases of dengue infection have been reported, against 206,000 in 2018. Meanwhile, cases of Zika and chikungunya have also spiked, by 44 and 47 percent, respectively. 

The Zika virus created panic worldwide in 2016, as it is linked to microcephaly in babies when mothers are infected during pregnancy. These babies’ skulls have circumferences smaller than normal and will likely suffer brain and eye damage.

Also fresh in the memory was one of Brazil’s deadliest-ever yellow fever outbreaks, another disease transmitted by the Aedes aegypti mosquito. Between July 2017 and February 2018, 237 people died from yellow fever. And there were a further 37 confirmed...