Understanding the Decline in Dengue Cases in Argentina: Preventing Mosquito Concerns for Future Seasons

2024-04-26 23:53:00
The decline in dengue cases in Argentina has been evident since week 13 of 2024, although concern remains over the presence of mosquitoes (Illustrative Image Infobae)

The outbreak of dengue in Argentina has so far reached total 333,084 cases and 238 deathsaccording to data from the Ministry of Health.

This count covers from late July 2023 to mid-April 2024, marking this season as a record for infections and deaths. To put the scale of this situation in perspective, it is important to note that it significantly exceeds the figures from the previous year, when there were 130 thousand reported cases and 65 deaths between July 2022 and the same month in 2023.

Currently, according to the latest epidemiological bulletin, a gradual downward trend has been observed in the number of cases across the country since week 13 of 2024, at the end of March. But despite the fact that temperatures have dropped in many parts of the country, which may affect the decline in infections, concern about the presence of mosquitoes still persists.

It is crucial to understand which species of mosquito are currently active and how to prevent the Aedes aegypti species, which transmits the dengue virus, from “taking up residence” in our homes. As winter approaches, specialists call for preventive measures to prevent the reproduction of these vectors, such as eliminating containers of stagnant water and protecting homes with mosquito nets, among other things.

There are species of mosquitoes that are currently active, especially Aedes aegypti, which transmit the dengue virus (Illustrative image Infobae)

In dialogue with Infobae, Dr. Hugo Pizzi, infectious disease doctor, epidemiologist and professor at the National University of Córdoba, contributed: “All epidemiological outbreaks have dynamics, that is, they begin, cases increase rapidly until they reach their peak, when they finally stabilize and begin to decrease. This is normally what happens in any epidemic outbreak situation. Here the situation is completely temporary. Mosquito activity decreased somewhat when the temperature was cold or relatively cold; tempered. Mosquitoes not only reduce activity, but also leave the surroundings around the house and enter the home.”

Therefore, according to Pizzi, “you have to be very careful in these circumstances, since the mosquitoes can be behind the curtains or in different places inside the house. So this does not mean that the problem has been solved; On the contrary, the activity has decreased a little, but we already see that the cases will increase again when the heat returns.”

“There are many female mosquitoes infected with the dengue virus that lay eggs,” the infection specialist continued. These eggs are already infected with the virus. That means that within five to six months, when there is a heatstroke, the new mosquitoes will hatch and the infected females will come out with the virus. This will continue to accumulate and increase the negative aspects of any epidemiological outbreak. Therefore, the concept is that there has been a decrease in cases, and it is true that mosquito activity has decreased, but with the return of heat, cases are starting to increase again.”

Pizzi emphasized the importance of maintaining preventive measures in homes (Getty)

“For cases to really drop in the next few weeks, the temperature needs to be below 12°C, because there could be a period of mosquito activity. We are compromising our future if we don’t take care of our environment and, fundamentally, our homes , because the females continue to lay eggs and most of them are infected, Pizzi said.

The epidemiology expert from the University of Córdoba added that “that is why it is important to clean the terrace well, throw stagnant water into the drains, scrub with a coarse sponge all the places where the eggs can be, among other things, these mosquitoes will appear in August or September”

Adrián Díaz, CONICET researcher at the Institute of Biological and Technological Research (IIByT, CONICET-UNC), pointed out for his part: “We have three abundant species in Argentina: Aedes albopictus, Aedes aegypti and Culex quinquefasciatus, in the south. Of these three species, the first to disappear with the cold is Aedes aegypti because it is a tropical mosquito, although it has adapted to temperate climates. “With persistent temperatures below 14 degrees, they are already dying.”

“The other species that disappears is Culex quinquefasciatus, which starts to lose activity when we are at more or less 10°C. Aedes albopictus is the last to go because it is a mosquito adapted to temperate climates. Obviously, in winter in Patagonia there are no mosquitoes. But in the summer and autumn in the southern latitudes it lives perfectly, and we still cannot talk about cold, said Díaz.

Aedes aegypti has adapted to human breeding sites and to identify odors that lead it towards sources of blood food, which requires preventive measures such as the elimination of internal breeding sites and the use of mosquito nets according to Adrián Díaz (Illustrative image Infobae)

At the same time, he said: “If we have two days of 13°C or 14°C and then a temperature of 20°C or 22°C arrives, the other mosquitoes start to activate again. Culex quinquefasciatus dies in the cold, both the adult and the larvae and eggs. As for Aedes albopictus and Aedes aegypti, they are flood mosquitoes and have eggs that resist drought and cold. Then the larvae and adults disappear, but the eggs remain and withstand the winter.”

“Aedes aegypti has adapted both to the nesting sites that humans have created for it, as well as to identify odors and thus perceive it as a source of useful blood food for them. To prevent them from entering homes, internal nesting sites must be eliminated. If you have vases, they can breed there and the best way to prevent them from getting in is to put mosquito nets on the windows and openings. In that way, we prevent them from entering, and we must also prevent them from breeding in the home, suggested the CONICET specialist.

It is important to recognize that in winter the mosquito vector does not completely disappear, as the larvae and eggs can remain in places with water accumulation, according to Teijeiro’s analysis (Getty)

Another professional consulted by Infobae was the infection specialist Ricardo Teijeiro, who is a member of the Argentine Society of Infectious Diseases. “Dengue cases in Argentina are going to fluctuate, as these are accumulated cases from previous weeks. This can lead to mortality peaks, given that some cases are patients who are hospitalized and treated with different outcomes. The current decline in cases is mainly due to the reduction in the development of the mosquito vector, which does not thrive in cold climates, so it does not reach the adult stage and therefore cannot transmit the disease,” the expert said.

And he added: “As cases decrease, the possibility of mosquito development also decreases. This is a seasonal phenomenon that occurs every year at this time. However, it is important to note that in winter the mosquitoes do not disappear completely, as the larvae and eggs remain in places where water accumulates. With the arrival of heat, these can develop, which represents a new risk for the next season. Therefore, it is crucial to work on prevention for the coming year.”

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