What is behind the new dengue epidemic in Brazil – 04/16/2022 – Equilíbrio e Saúde

Since January, Brazil has recorded 323,900 probable cases of dengue and 79 deaths from the disease.

The numbers, available in the latest epidemiological bulletin from the Ministry of Health, reveal an increase of 85.6% in infections by this virus, transmitted by the bite of the mosquito. Aedes aegypticompared to the same period in 2021.

In some parts of the country, the situation is worse: in the Midwest, the growth compared to last year was 242%. So far, the region has recorded 648 cases per 100,000 inhabitants – the South appears in second place, with 198 cases per 100,000.

Among the five most affected cities, three are in the Midwest: Goiânia (25,100 cases), Brasília (19,200) and Aparecida de Goiânia (4,600). Palmas (7,500), in Tocantins, and Votuporanga (4,700), in São Paulo, complete the list.

“What is observed this year is an expressive activity of dengue in some parts of the country, in particular in the axis that goes from Tocantins to Santa Catarina, passing through the Midwest and the western portion of São Paulo”, interprets the biologist and epidemiologist. Cláudia Codeço, researcher at Fiocruz (Fundação Oswaldo Cruz).

But what is behind this scenario? And what can be done to combat it? Specialists heard by BBC News Brazil explain that a series of combined factors contributed to the increase in dengue precisely in this period.

The ingredients of an epidemic

“We had an especially favorable climate for dengue this year, with intense and prolonged rains”, recalls Codeço.

Since the end of 2021, when summer began, several Brazilian cities have registered many storms, related to phenomena such as La Niña and climate change.

To Aedes aegyptirains are synonymous with standing water, a place where mosquito eggs hatch and larvae develop until they reach the adult stage.

“Usually, when the month of December arrives and we begin to notice a great concentration of Aedesit is already possible to predict that March and April will be bad, with many cases of dengue”, observes infectious disease specialist Celso Granato, director of Fleury Medicina e Saúde.

But at the turn of 2021 to 2022, projections were hampered by two other health crises.

At the same time, Brazil faced an epidemic of H3N2 influenza, which caused a significant increase in influenza cases, and the spread of the omicron variant of the coronavirus, behind records in infection numbers.

“Dengue surveillance systems were greatly impaired, since in these last two years there was an almost absolute focus on the Covid-19 pandemic”, adds the doctor, who is also a professor at Unifesp (Federal University of São Paulo).

Still in relation to the pandemic, the lower number of infections in 2021 also has to do with periods of greater social isolation, which reduced the movement of people through cities.

“And it is worth remembering that we had a major dengue epidemic in the country in 2019, so a new increase was already expected from 2022, since the waves of the disease are cyclic”, says physician Melissa Falcão, from the Brazilian Society of Infectious Diseases.

Finally, Codeço highlights that “we have an impoverished population, with housing difficulties, and we see the precariousness of cities”.

“All this makes it difficult to control vectors that transmit the disease”, explains the specialist, who coordinates InfoDengue, an initiative by Fiocruz and FGV (Fundação Getulio Vargas) to monitor diseases related to Aedes.

“It is also important to observe the spread of the disease to the south of the country, where it was little active or almost non-existent. This expansion may be related to climate change and the adaptation of the mosquito itself”, adds the epidemiologist.

The trend, according to what happened in previous seasons, is that dengue cases continue to rise in the country at least until the middle of May. From there, with the arrival of lower temperatures in the South, Southeast and part of the Midwest, records should fall again.

“Dengue numbers tend to be higher during summer, because of the high temperature and the amount of rain, but the period of rise of the disease starts in October and goes until May. The trend is a more accentuated reduction in the number of cases to from June”, stipulates Falcão.

“Even so, dengue prevention care should take place throughout the year”, emphasizes the infectologist.

Having identified the causes of the problem, what can be done to deal with this hidden epidemic of dengue?

The authorities’ response

As there is no approved vaccine against dengue, the most effective preventive actions involve eliminating the breeding sites of the transmitting mosquito – and ideally, this work should begin in January or February, when the eggs begin to hatch.

“With the pandemic, there are fewer resources left to fight the Aedes“, says Granato.

Now in April, there are fewer actions that can be done. “It remains to bet on the smoke, which helps to inhibit the adult mosquito”, completes the infectologist.

Another important attitude is to expand and strengthen public health services, to be able to accommodate patients with dengue complications.

The epidemiological bulletin of the Ministry of Health this year counts 233 episodes of severe dengue and another 2,800 with warning signs. So far, 79 deaths from the disease have been recorded.

Granato is also concerned about the recurrence of dengue in regions that have had outbreaks and epidemics in the recent past.

“There are four serotypes of the virus, which means that the same person can catch dengue four times. The problem is that having a second or third case of the disease increases the risk of suffering from the most severe forms”, he explains.

“And we have some regions, especially in the northwest of São Paulo, that have been experiencing dengue outbreaks since the 1980s. This represents a higher risk of death in these places”, he continues.

BBC News Brasil contacted the state health departments of Goiás, Distrito Federal, Tocantins and São Paulo, locations with the most affected cities so far.

The Federal District Secretariat stated that it always promotes actions to combat Aedes in all administrative regions.

“We perform an analysis of the incidence of cases by region and also of the cities where there is a greater presence of the mosquito. After this analysis, the regions with the greatest increase begin to receive an intensification of actions, including the use of the Heavy UBV [fumacê]which is just one of the strategies used to combat the mosquito.”

The representatives of Goiás admit that “the advance of cases puts the State on alert for the possibility of an epidemic by dengue”.

“The State Health Department links the expressive increase in the infestation of Aedes aegypti and the number of cases of diseases caused by the vector to the intensity of the rains and the low adherence of the population to clean their homes.”

The São Paulo secretariat highlighted that the number of cases in the state is lower (or slightly similar) in 2022 compared to 2021, despite the bad situation in some cities this year.

“According to the guidelines of the Unified Health System, field work to combat the mosquito that transmits dengue is primarily the responsibility of the municipalities.”

The State Department of Health of Tocantins and the Ministry of Health were contacted, but did not send responses until the closing of this report.

Falcão understands that public policies need to reinvent themselves and bet on new technologies to combat the mosquito. “We have already seen that what has been done over the last few years has not had an effect.”

“Another key point is the investment in infrastructure, in basic sanitation, leading to an increasing share of the population access to water supply, sewage system, garbage collection and rainwater drainage”, lists the doctor.

What can you do

In addition to public policies, experts call attention to individual responsibilities in combating dengue.

Here come those classic recommendations to avoid any unprotected stagnant water reservoir at home. The mosquito can use large spaces as breeding grounds, such as water tanks and open pools, even small objects, such as bottle caps and plant pots.

It is worth cleaning the backyard and balcony, paying special attention to deposits, gutters and objects that are outside and can accumulate rainwater.

Installing screens on doors and windows or using repellents on the skin are attitudes that can also help.

Finally, it is important to be aware of the symptoms of dengue, such as fever, tiredness, redness in parts of the body, itching and pain in the head, muscles, joints or behind the eyes.

After the diagnosis of the disease, the recommendation is to rest, focus on hydration and, if necessary, use medicines that relieve some of these discomforts.

“Everyone needs to know the signs that the disease may be progressing to the most serious forms. The main ones are vomiting that is difficult to control, fever that does not decrease, belly pain and bleeding”, Granato lists.

“In this situation, it is essential to seek an emergency room as soon as possible”, concludes the doctor.

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