Rio Grande do Sul has become an inverted portrait of dengue in Brazil. If before the cold kept Aedes aegypti under control, now the mosquito that transmits the disease causing the disease has found a favorable climate to spread throughout the state. The disease does not stop moving forward: until May 8, there were 15,643 confirmed cases and eight deaths.
The current epidemic, although even lower than last year, grows fast: the transmission rate is already from 2.08, and 474 gaucho municipalities are infested with mosquitoes, two more than in 2024. In practice, this means that the virus grows in a rhythm of expansion similar to the first months of 2020. For specialists, the scrip of clear: urban inequality and structural failures are redesigned the map of the map of the map Dengue – And the south entered the route once and for all.
According to public health researcher Diego Ricardo Xavier, from the Institute of Communication and Scientific and Technological Information in Health of the Oswaldo Cruz Foundation (ICICT/Fiocruz), dengue is a disease that is totally associated with climate issue.
“We have seen dengue entering the south, where there were no epidemics so frequent, because the climate barrier prevented. Now, besides moving to subtropical regions, it is climbing the mountains. If the world continues to warm, we can have dengue epidemics even in Europe and the United States,” he says. In some European countries, such as Spain and France, there are already records of indigenous cases – locally acquired infections, unrelated to trips to endemic regions.
Until mid -April, Infodengue, Fiocruz’s platform, which is one of the main Brazilian arbovirus monitoring systems (mosquito -transmitted viruses), recorded 1,757,065 suspected dengue cases in the country. Of these, more than half (67.69%) are classified as probable, a variation of almost 30% compared to 2024.
Epidemiologist Claudia Codeço, coordinator of Infodengue, explains that climate variables have been considered in the report and already point out evidence of the impact of global warming on disease expansion to historically protected areas.
“These regions are observing longer periods of favorable climate, especially with milder winters and the early arrival of spring. Even small changes can lead to large dengue increases as they allow viruses to maintain their transmission cycle during winter and quickly reproduce when spring reaches,” he details.
The current scenario, with outbreaks in regions previously considered poorly vulnerable, is the most visible result of this new climate dynamics. And understanding how dengue spread around the world helps to scale the current challenge.
A mosquito that transmits four types of viruses
Mosquito Aedes aegyptidengue is a disease caused by family viruses Flaviviridaethe same as the yellow fever virus and zika. There are four different serotypes-Denv-1, Denv-3, Denv-3 and Denv-4-and the infection for one of them generates immunity only against that type, leaving the organism vulnerable to others.
The transmission cycle begins when the female of the mosquito, when chopping an infected person, acquires the virus and starts to transmit it to other individuals throughout life. The most common symptoms include sudden fever, headache, pain behind the eyes, body and joint pain, reddish spots on the skin and prostration.
“Also called ‘Break Fever’, dengue may initially seem like a common viral infection, but it requires extra attention,” warns infectologist Emy Akiyama Gouveia of the Israeli Hospital Albert Einstein.
Generally, the disease is self -limiting, with spontaneous recovery. But it can evolve to serious forms. Warning signs include bleeding, intense abdominal pain, persistent vomiting, shortness of breath, dizziness and mental confusion. “These signs usually appear at the stage when fever begins to give in, between the third and seventh day of the disease,” explains Gouveia.
The diagnosis is mainly made from clinical evaluation, without the need for laboratory confirmation in some cases. Rapid tests and blood tests may be asked to confirm the infection or monitor changes in cases suspected of aggravation.
The doctor stresses that self -medication is a risk and that proper hydration is critical to avoiding complications. “Delay in liquid replacement is one of the main factors of unfavorable evolution,” he warns.
Despite the accumulated knowledge, controlling dengue follows a challenge in Brazil. “THE Aedes aegypti It is ubiquitous in the country, ”says Gouveia. She points out that although vaccination is advancing, coverage is still low and, by SUS, restricted to specific groups of the population.
Millennial disease
The first descriptions of an infection with dengue -like characteristics date back to ancient China between 265 and 420 AD during the Chin dynasty. At the time, the disease was known as “water poison”, in a popular association with flying insects near aquatic environments.
Centuries later, similar outbreaks were recorded in the French West Indies and Panama in the 17th century, and epidemics were described in Asia, Africa and North America between 1779 and 1780. Mosquito transmission was only confirmed in 1906; and the virus, identified the following year.
In Brazil, the Aedes aegypti It would have arrived during the colonial period, brought from Africa in slave ships. The first reports of cases in the country emerged in the late 19th century in Curitiba and in the early 20th century in Niterói (RJ), according to the Oswaldo Cruz Institute. But it was only from the 1940s that the perception of dengue as a public health emergency gained strength.
In the following decade, the Aedes aegypti It was even eradicated from the country as part of the efforts against yellow fever. But the relaxation of measures in the following years made him return.
Global warming and the increase of cases
In recent years, climate change has aggravated the scenario. , in the United States, presented at the end of 2024, estimates that global warming account for approximately 19% of dengue infections in the world. Increased average temperature, especially in the range between 20 ° C and 29 ° C, creates ideal conditions for the virus and can lead to growth of up to 200% in cases in endemic regions in the coming decades. Today, about 257 million people live in areas where dengue incidence can double in 25 years.
In Brazil, projections follow the same line. , federal government platform that measures the vulnerability of municipalities to climate change and proposes adaptation actions, half of the municipalities should have a high or very high risk for diseases transmitted by the Aedes aegypti By 2030. Estimates combine variables such as temperature, rainfall, deforestation, population density and access to basic sanitation.
In addition to geographical expansion, the pattern of epidemics has changed. Once concentrated in the summer months, dengue transmission now extends almost all year rounds in various regions, driven by out -of -season heat waves. According to a survey by Fiocruz’s Climate and Health Observatory, the interval between epidemics practically disappeared: the years 2022, 2023 and 2024 recorded consecutive outbreaks.
Events like El Niño – which warms above normal the waters of the Pacific Ocean on the Ecuador line – also had an impact. “When it had El Niño, summer started before. In September it was already infernal heat. This out -of -season heat, combined with rain and more available breeding sites, made the mosquito reproduction time to increase,” says Xavier of Fiocruz.
Structural confrontation
Despite the critical scenario, new dengue -fighting strategies offer promising perspectives. In addition to advances in clinical management – with updating the hydration protocols and early diagnosis by the Ministry of Health, which now initially treats all arboviruses such as dengue – the focus turns to the confrontation of the vector and the expansion of vaccination.
One of the bets on mosquito control is the Wolbachia project. Bacteria, which occurs naturally in about 60% of insects, was introduced in the Aedes aegypti to block your ability to transmit the virus. Initiatives in Indonesia, Australia and Colombia showed reductions of more than 75% in the cases of dengue in the target areas.
In Brazil, the program is developed by the non -profit organization World Mosquito Program (WMP) in partnership with Fiocruz and the Ministry of Health. It is currently present in five cities, expected to expand to six more. In Niterói, analyzes indicate a drop of about 70% in the cases of dengue, 60% in Chikungunya and 40% in Zika in regions where mosquitoes were released.
In the field of immunization, the perspectives are also encouraging. The Qdenga vaccine showed more than 80% effectiveness against the four serotypes and expanded prevention options for people between 4 and 60 years. There is also great expectation by the immunizer of the Butantan Institute, developed over a decade and still awaiting approval by the National Health Surveillance Agency (Anvisa). With a unique dose and effectiveness of 79.6%, the national vaccine may be incorporated into the National Immunization Program (PNI).
For experts, however, these solutions will only have real effect if there is coordinated planning and action. “The timely response to dengue requires preparation, with organized coping plans, a trained response network and a warning system,” says the Infodengue coordinator.
In addition, it is urgent to attack the structural roots of the problem – especially in the context of climate change and social inequalities in Brazil. Diego Xavier quotes the example of the dengue epidemic that hit São Paulo during the 2014 water crisis. “A lot of people started to accumulate water. This generated an artificial breeding ground and dismantled classic models that claimed that, to have dengue, it was necessary heat and rain,” he explains.
The most affected regions were precisely those with worse access to water. “We will no longer be able to reverse the situation, it has gone to vinegar. What we can do now is trying to reduce the size of the impact,” says the researcher. For him, the most viable is to invest in urban infrastructure – such as sanitation and housing – and educational campaigns, following the example of Asian countries such as Singapore and Vietnam, who have managed to control the disease.
In addition, health services need to be empowered in localities that historically did not face the disease and guide the population to combat the vector. “Education and solve base problems are important advances to avoid epidemics, but they are not a silver bullet. We have to use everything we have,” concludes Xavier.
