María Romero’s lungs were filled with fluid when she entered into intensive care in 2009 with a life threatening case of Dengue fever. Even though the disease was well known in tropical places, in the temperate region of Central Argentina it was unprecedented.
“I was with a respirator, my face was swollen, all my body hurt and my hair was falling out, I was bad”, said Romero. She was only 15 years old at the time. At that moment she had heard of the virus, but she never thought she would be infected with it.
Everything started with a strong fever and some red spots all around her legs. All of a sudden, she ended up at the hospital for more than a month. “I was really thin and I had to lie down because if I stood up, a headache started”, explained.
María was one of the cases detected during the first Dengue outbreak in Córdoba in 2009. Before that year, Dengue was found only in areas with subtropical climates, mainly in the northern part of Argentina. Now, climate change has moved this disease to temperate regions such as Córdoba.
Dengue is a type of disease transmitted by the Aedes Aegypti mosquito. When an infected mosquito bites a human, it typically causes strong fevers and nausea. In more severe cases, the illness can be life-threatening and requires immediate medical care. The case of María was one of these, most of her organs were affected, and at some points, doctors were afraid she could not make it through.
Climate change is turning many temperate regions —like Córdoba— into subtropical regions, explained biologist and ecologist Irene Wais, from the Argentinian Academy of Environmental Science and professor of Buenos Aires University. This is altering the distribution of the Aedes Aegypti mosquito, she added.
In recent years, Dengue also arrived in another temperate country in the Américas: Uruguay. In 2016, the country detected the first autochthonous case in 100 years. Before that, they only had noticed imported cases from travelers that had been in endemic regions and had returned to the country.
The Minister of Health of that period, Jorge Basso, suggested climate change played a role in the change in the appearance of new cases.
Recently, a study made in Costa Rica analyzed the influence of socio-economic, demographic, geographic, and climatic factors on Dengue incidence between 1999 and 2007. The publication asserted that temperature was the variable that most affected the incidence of this disease, as explained in a CEPAL report published in 2021.
Wais affirmed that, as new regions become warmer, the habitat range of the mosquito expands. Other factors such as urbanization and changes in land use also contribute to the mosquito’s displacement.
The expansion of Dengue influence affects primarily low socioeconomic level populations, asserted CEPAL. This sector is less adapted to the effects of climate change, as they usually have inadequate water services, bad management of solid waste, and deficient urbanization conditions.
“Together with global mobility and urbanization, climate change is a major driver of the increase in the number of Dengue virus infections” reads the report. This is also happening with other diseases such as Malaria, and Colera.
Outbreaks in Cordoba
The first outbreak of Dengue in Córdoba occurred in 2009. Before that year, Dengue didn’t exist in the province. Now, it has become a reality in the region, interlinked with cases in other countries.
Claudio Guzmán, the coordinator of the vector program of the Ministry of Health, explained that outbreaks in other countries affect when the first imported cases will be detected in Argentina. Because of this, the peak month of cases can change each year, he said. This is because Dengue is not endemic in Córdoba, always the first case is necessary for a traveler that has been in a circulation zone.
Added to the regional context that affects the disease in Argentina, different studies suggest that changing temperature is in fact modifying mosquito behavior around the world. “Alterations in temperature and humidity driven by climate change have modified the life cycle of the Aedes aegypti”, explained CEPAL.
This is also happening with Malaria, as The Lancet report indicates. A study on this illness confirmed that the transmission season has grown around the world due to climate change and that less developed sectors were some of the most affected.
In Córdoba, the following years after 2009, more cases appeared. The biggest peak in Argentina, and also in all of the Americas, took place in 2019-2020 when more than 55.000 cases were reported in the country. The largest number of infections at the time was detected in Córdoba. It was the first time that there were deaths in the province because of Dengue.
The best way to prevent Dengue infections is by raising awareness among citizens because the mosquito has domiciliary habits. “Governments have a responsibility, but also do people. Governments have to empower people for the preventive practices”, pointed out Miguel Díaz, head of Hospital Rawson, the specialized health center for infectious diseases.
In Córdoba, the provincial government implements prevention campaigns in the transmission season of the virus. Members of the local Ministry of Health visit homes in risky neighborhoods and give information about Aedes Aegypti and the illnesses that it carries, including Dengue, Chikungunya, and Zika.
They teach people how to eliminate potential mosquito breeding sites and how to prevent bites. Neighbors also learn how to identify symptoms of these diseases.
The elimination of young mosquitos is the action that has had more impact, explained Guzmán. The flying Aedes Aegypti that people see represents only 10% of the mosquito’s live population, the other part is constituted by larvae and young specimens.
Even though there is no data available on the effectiveness of these campaigns in Córdoba, they are one of the preventive actions recommended by the Pan American Health Organization. The Institute asserts that the fight against the illness must urge communities and mainly families to make “behavioral changes and sustainable actions”.
On his behalf, Díaz affirmed that seasonal vigilance in neighborhoods is a good measure, but believes other permanent actions —such as increased surveillance— are needed.
Tropical diseases incoming
Rising temperatures due to climate change are expanding the range of diseases like Dengue, which are often known as diseases “carried by vectors”. In this case, the mosquito acts like a contagious agent. If its range expands, the disease travels with it.
According to Claudio Guzmán, tropicalization is responsible for the appearance of Aedes Aegypti in the Córdoba “This is happening also with the triatomine bug”, which is the vector of Chagas disease.
This illness affects 6–7 million people worldwide, mostly in Latin America. In the first phase, symptoms are mild and unspecific, but in a chronic phase, the infected person can develop cardiac or digestive alterations.
Talking about Dengue, the World Health Organization (WHO) explains that the optimum temperature for the mosquito to incubate and transmit the virus is between 25° C and 28° C degrees. The temperature must be constant from eight to twelve days.
The frequency of precipitation and humidity levels can also alter the mosquito’s life. Additionally, stuck water —as in swamps and ponds— is needed, because it’s the space where the mosquito’s larvae grow.
An increase in urbanization is also influencing the expansion of the Dengue virus, experts said. “You have more people, ergo more transmissibility. (…) In cities, you have more places where water can get stuck because sunlight does not enter”, Wais explained.
According to Wais’s view, Aedes Aegipty will continue to adapt even if the temperature rise continues. Mutations in mosquitos are frequently reported, something that will make the mosquito more resistant to the local weather conditions, she said.
“In the animal kingdom, insects are the group that has diversified the most. At any change, they can adapt their physiology and their life cycle”, explained the biologist.
María Romero is aware that many more cases of Dengue were reported in the province after her own infection. She also notices that there are more preventive campaigns than when she got the disease. She remembers seeing an alert letter about Dengue in the airport and fumigation trucks in her neighborhood.
In most cases, the first Dengue infection is a level form of the disease that does not present many symptoms. Because of the gravity of her case, doctors believe that when María was hospitalized, it was in fact the second time she got infected.
When she recovered, she continued with her life and was able to fulfill all her personal projects, but affirms that having Dengue at the age of 15 was a traumatic experience. As climate change threatens to expand the disease, María believes that more awareness is needed, as there are still a lot of people exposed to the expanding disease.