Dengue: Brazil cases increase nearly 86% in 2022, but danger is to come, researchers warn

Publicação: 10 de May de 2022

Between January 02 and April 02, 323,900 suspected cases of the disease were recorded, 85.6% higher than in the same period of 2021

Midwest is the region with the most cases, with 648/100 thousand inhabitants, followed by the Southern region, with 198.5 /100 thousand inhabitants

Suspected cases of dengue remain on the rise in the country compared to 2021, according to Epidemiological Bulletin Vol.53, Nº13, released by the Ministry of Health. The document reveals that between January 02 and April 02, 323,900 suspected cases were recorded, 85.6% higher than in the same period last year.

The Midwest was the region that recorded most cases of arbovirus (648/100 thousand inhabitants, in which diagnoses skyrocketed 242.7% in the first thirteen weeks of this year compared to the same time in 2021. Goiás leads the explosion of diagnostics, with 71,652, more than the entire Southern region. Of this total, 25,180 cases were reported in Goiânia. The capital is the city with the most infections in Brazil, followed by Brasilia, with 19,284. In all, the region counts 108,258 cases, representing 33.4% of the records throughout the country. Next are the South regions, 198.5/100 thousand inhabitants, North, with 127.8/100 thousand inhabitants, Southeast, 106.2/100 thousand and Northeast 62.4/100 thousand inhabitants. On the so-called severe dengue (SD), the Bulletin indicates that 233 cases were confirmed in this period, in addition to 79 deaths. São Paulo is the state that recorded the most deaths from the disease, totaling 29; followed by Goiás, with 9, and Bahia, with 8.

Dr. Luciano Pamplona, a researcher and professor at the Department of Community Health at the Federal University of Ceará (UFC), explains that in recent years, probably due to the Covid-19, pandemic, there has been a reduction in the number of reported cases of various diseases; as well as dengue. “In 2022, in addition to the significant increase in rainfall, we have almost two years without the visit of health agents (endemics) in people’s homes. Control activities have been suspended due to the pandemic and there are reports of high levels of vector infestation by Aedes aegypti. All these factors contribute to the transmission, not only of dengue, but also chikungunya and Zika. About the Northeast region, Pamplona reports that there is a significant increase in the transmission of the disease at this time, in addition to cases of chikungunya, which should put people and managers on alert. For him, the intensification of rainfall in this period and the long time without home visits by health agents contributed significantly to the current scenario we live in.

Dr. Mauro Shugiro Tada, director general of the Tropical Medicine Research Center of the State Health Department of the State of Rondônia (CEPEM-SESAU), agrees with Dr. Pamplona and adds that the accumulation of garbage in wasteland and closed homes helped significantly in the proliferation of the transmitting mosquitoes. The researcher points out that in the North region, the month of March signals the end of the rainy season and begins an increase in mosquito breeding sites that peak in April and with this, transmission occurs more intensely, so if the rainfall continues, the outbreaks will too. Regarding the situation in the North, Dr. Tada says it is very peculiar due to the low population density in which only large cities (capitals) mainly verticalized such as Manaus and Belém, have the same projections as other regions of Brazil. “The other medium and small cities in the interior of the Amazon, the outbreaks are localized and of lower intensity,” he said.

The epidemiologist and professor at The São Leopoldo Mandic College of Campinas, Dr. André Ribas Freitas, adds that the return of the circulation of people leads to an increase in the circulation of the virus and with this the possibility of transmission grows plenty. “This year, the occurrence and increase of cases occurred late, in March and April. However, it was not possible enough dynamics to form a major epidemic, although isolated points presented outbreaks, but it was not a generalized situation, however 2023 may be different,” he points out. Moreover, he does not rule out the possibility of a chikungunya epidemic next year. “This must be on the radar, since, for example, the interior of the state of São Paulo has never been significantly affected by this disease, and therefore has almost the entire susceptible population,” he said. For him, the larger municipalities of the Northeast and Southeast regions, which were not affected this year, and which have a history of dengue epidemics, deserve great care, since the possibility of this happening is an important reality and should be considered.

The Superintendent of Health Surveillance of Goiás, Dr. Fluvia Amorim, recalls that when it comes to dengue, it is not only a factor that causes the epidemic or that causes cases to decrease, but rather a set of factors (climatic, lack of agents, formation of pockets, etc.). “Unfortunately, it is a set of factors that culminate in what we are seeing in Goiás, in the Midwest region and in other regions of the country. In addition, the Midwest region has a favorable climate, it is hot almost all year round, with high rainfall rates, especially in the summer, which also favors the proliferation of Aedes aegypti, and consequently leads to increased transmission,” she says. “When evaluating the incidence of dengue in a state or region, one should take into account the capacity of epidemiological surveillance of this site, the more sensitized, the greater the importance of notification with the assistance units is developed, whether private or public, the greater the number of notifications”, he points out. According to her, it is important that municipal departments and managers alert health professionals to the occurrence of dengue cases, both in the surveillance part and in the clinical management part. “What scared us in Goiás and that may be happening in several other regions of the country is that many municipal managers decided to hire outsourced companies to combat the vector and, thus, we do not know which insecticide is used, under which dilution, if it is being applied in the correct period; in fact, we have already verified the application at not recommended times of the day. To prevent mosquito resistance to the insecticides used from occurring, we are editing in the state a resolution to regulate this type of service,” says Dr. Amorim.

Dr. Cátia Favreto, a nurse specialized in Public Health, recognizes that Rio Grande do Sul has a very significant increase in dengue cases, where 2022 has more notifications in a historical series since 2010. “Rio Grande do Sul is following a trend of increase in cases as the rest of Brazil,” she said. According to her, taking into account the historical series, May should represent the beginning of the decrease in records. “However, we cannot predict, because, as 2022 is being a differentiated year in number of cases, we can still be confirming these,” he notes. On autochthonous cases, contracted within the state, there was also a significant increase. The data, which is updated daily, is available in this arbovirus panel.

Dengue and chikungunya co-infection

Dr. Amorim acknowledges the severity of the situation in the Midwest, a region that historically has always reported the highest incidence of dengue. However, according to her, in May 2021, there was an increase in cases of chikungunya and today the state is undergoing an explosion not only of dengue, but also of chikungunya, including many cases of co-infection. “We noticed that health professionals and the population claimed this dengue seemed to be stronger and so we decided to check which virus was prevalent. By performing virological surveillance, we identified the DENV-1, virus, which in the literature, on the virulence scale, is the least virulent. But we also have in circulation, in a smaller number, the DENV-2 virus,” she describes. What draws attention and worries in this explosion of cases, according to her, is the number of reports in children, including deaths. “We are monitoring the cases, performing virological and genomic surveillance and trying to sequence some samples to know what is the phylogenetic lineage of these viruses to understand a little more what is happening in the state of Goiás,” she ponders.

Danger is still to come

Experts warn that by 2023 the situation should get a little more complicated. “It has been about four years since the last major epidemic, moreover, viral circulation has become very low due to social distancing, leading to a general drop in collective immunity. The possibility of a new epidemic next year is certainly real, especially in the Southeast region,” says Dr. Freitas. Dr. Pamplona also warns that 2023 may be a year with a high transmission rate of these vector diseases transmitted by Aedes aegypti due to the long time without adequate control. “In addition, we have cohorts of new people who have never been exposed to some serotypes and recirculation of DENV-2 in various regions” she argues.

Measures

The problem of dengue can practically be solved with the vaccine under test if it obtains the expected result in this phase III (around 90% effectiveness). Meanwhile, the best form of prevention is inside the households. Changes in population behavior to eliminate breeding sites make control measures much more efficient. We have a high chance of increased cases of dengue, Zika and chikungunya in 2023 and this can be improved if there is population engagement. The application of UBV (Smoking) serves for the chemical control of Aedes, but alone does not solve an epidemic. “Basic Sanitation, as occurs in civilized countries, is the solution of the moment, besides, of course, solving all water-transmitted diseases. The importance of this, too, is that it was thought that the dengue mosquito reproduced only in collections of still and clean water, we know today that it reproduces intensely in ‘black pits’ and the sanitary issue in Brazil is very bad, especially in the Amazon and the Northeast”, concludes Dr. Tada.