The climatic phenomenon El Niño caused the outbreak of dengue fever in Brazil. This opinion was expressed by the director general of the World Health Organization (WHO), Tedros Adanom Ghebreyesus. "The current outbreak of dengue fever is caused by El Niño," - quotes his words Observador. This natural phenomenon affects weather patterns and contributes to an increase in temperatures both on land and in the oceans, which leads to an increase in the number of yellow fever mosquitoes (lat. Aedes aegypti), the vectors of the fever, the publication explains. The head of WHO, during his three-day visit to Brazil, called the dengue outbreak in the country a "serious challenge." According to data from Brazil's Ministry of Health cited by the newspaper, the South American country recorded more than 1.6 million cases of dengue infection and 1,094 deaths in 2023, "a record."

Rio de Janeiro Mayor Eduardo Paes had earlier declared a state of emergency in the city due to the fever epidemic. This happened a few days before the start of the world-famous carnival. Dengue fever is a dangerous tropical disease. The disease came to Brazil in the late 19th century from Southeast Asia. Before the vaccine was available, the only effective way to combat dengue epidemics was to control the habitats of its vectors - mosquitoes.