Every summer in Tucumán there are always some suspected cases of dengue, the pathology transmitted by the Aedes aegypti mosquito. Every so often, a more serious outbreak of the disease is recorded. Our province has already had three epidemics, the most important was in 2020, when 7,866 patients with the pathology were reported. Before, in 2009, 1,749 had been reported and in 2016, 274.
However, there are a large number of cases that go undetected. This has become clear from a national study that showed that 10.7% of Tucumans (approximately 171,000 inhabitants) had dengue at some time in their lives.
The figure is even much higher than what is calculated in epidemics: that for every confirmed case there are another 10 that are not reported and that are part of an underreporting. They are not detected because patients are asymptomatic or because doctors do not order a specific test for the disease.
The national study, which was coordinated by researchers from the University of Buenos Aires and Conicet with the contribution of colleagues from several provinces (including Tucumán), showed that 10.7% of Tucumans aged 18 or older have antibodies against the dengue virus, indicating that they were once infected.
The work was published in the Journal of Clinical Virology and is the first study on the prevalence of dengue in the areas of the country where the mosquito that transmits the pathology lives.
To carry out this epidemiological work, the researchers analyzed 1,530 samples provided by a dozen blood banks from more than 80 cities in central and northern Argentina. This is a representative collection of the adult population living in the regions where the infection vector is present, as explained Federico Di Lelloresearcher at Conicet and member of the Institute of Research Institute in Bacteriology and Molecular Virology (Ibavim).
The professional said that in the case of our province, the samples that were analyzed were from San Miguel de Tucumán, Concepción, Las Talitas, Banda del Río Salí and Monteros. The data obtained are a representative sample. It can be inferred that one out of every 10 Tucuman over 18 years of age has already had contact with the dengue virus. What does that mean? That a good part of the population, although they do not know it, is at risk of contracting a severe form of dengue that occurs mainly among those who have already suffered from the disease.
The values detected in Tucumán are slightly lower than the national average, which is 14.2%. And even lower than the percentages found in Misiones and in the Metropolitan Area of Buenos Aires, where 24.5% of the population already had dengue, according to this work.
In any case -according to Di Lello- all the values are high if one takes into account the epidemiological bulletins, where the number of registered cases appears.
This research is important because it makes it easier to know the percentage of inhabitants who had dengue and, if possible, with what serotype, the expert remarked. “This allows us to be better prepared for future outbreaks that are sure to occur in the next few years,” he explained.
In telephone contact with LA GACETA, Di Lello recalled that dengue has four serotypes, from DEN 1 to DEN 4. Therefore, knowing the seroprevalence is an essential indicator to know what is the risk of serious dengue cases occurring. The most complicated pictures of dengue occur when the person is infected for the second time, if it is with a different serotype than the one from the first infection. It happens that in this second infection the antibodies, instead of defending the organism, help the virus to enter the cells, he explained.
“That more serotypes of the virus circulate and that there is a good part of the infected population is a risk of having more serious cases, more hospitalizations and a greater number of deaths,” he said.
Dengue outbreaks have been expanding periodically every four or five years, he specified. Between 1997 and 2008, only a total of 3,500 cases were reported. By 2009 they rose to 28,000. In the 2016 outbreak, 49,000 were reported and in 2020, there were 57,000 cases.
There are more and more cases and outbreaks appear more frequently, Dilello said. He considered that for many years Argentina had a kind of “luck”. “In neighboring countries, such as Brazil and Paraguay, each year the circulation of the four different serotypes of this virus is confirmed. And, for some reason, Argentina was ‘getting rid of’ and recorded mostly the prevalence of dengue type 1”. However, in 2020 luck ran out: in the last outbreak it was determined that a good part of the infections were due to serotype 4.
“Maybe next year or in the next two or three years the country will experience a major outbreak again. Everything will also depend on the situation in the countries of the region and tourism. We have to take advantage of the time to do prevention because what is clearly seen is that the mosquito is gaining a lot of ground. You have to multiply the tasks. Social responsibility is very high in the task of cleaning and disposing of houses. But the State must also control more, fumigate, educate and carry out more campaigns to reduce the presence of the mosquito as much as possible”, warned Di Lello.
Diego Flichman, from the Institute for Biomedical Research on Retroviruses and Acquired Immune Deficiency Syndrome (Inbirs); Gabriel Garciafrom Ibavim, and Federico Martinezfrom the Norberto Quirno Center for Medical Education and Clinical Research (Cermic).