A study by Brazilian researchers concluded that seven states in the country are at high risk of experiencing outbreaks of zoonoses, diseases transmitted from animals to humans.
In the Federal District and 11 others, the risk is medium and, in the other units of the Federation, low, according to research published this Wednesday (29) in the journal Science Advances.
Zoonoses are well known – monkeypox is one such case. One of the factors that most favors the appearance of this type of disease is the entry into forest areas.
Hugo Fernandes-Ferreira, professor at the State University of Ceará and one of the authors of the article, explains that zoonoses are the result of a process of continuous mutations until a pathogen – any organism that causes a disease – has the capacity to infect humans.
“This possibility grows when contact increases, which occurs by facilitating access – that is, deforestation – and direct contact [com animais silvestres]”, says Fernandes-Ferreira, who is also a biologist.
In the new study, invasion of environmental regions were taken into account. Biodiversity was also observed, since the greater the presence of different species of living beings, the greater the risk of disease transmission.
In addition, the researchers looked at socioeconomic issues and the ability to respond to risky situations to understand the chances of new outbreaks appearing.
“There are several crises that turn our country into a potential incubator. They are environmental, socioeconomic crises, increase in deforestation, unemployment, food insecurity. All this increases the degree of exposure of people to these pathogens”, says Gisele Winck, biologist associated with Fiocruz and lead author of the article.
The researchers used data collected between 2001 and 2019 from nine zoonoses already known in Brazil to carry out the research analyses: Chagas disease, yellow fever, spotted fever, cutaneous and visceral leishmaniasis, hantavirus, leptospirosis, malaria and rabies. Looking at the patterns of spread of these diseases, the authors measured the risks of new outbreaks.
Aspects that influence the pattern of disease spreads in Brazil were seen: loss of vegetation, richness of mammals, isolation of municipalities, little urban vegetation and low vegetation cover. “These five points explained 80% of the pattern seen in the emergence of diseases in our country. So they are the main factors that contributed to the pattern we saw”, says Winck.
All states and the Federal District were divided into three categories: low, medium or high risk. One of the most critical regions is the North, where Pará has medium risk and all other states have been categorized as high risk. This pattern can be explained by the intense deforestation of the Amazon.
“In Brazil, especially in the North region, there is deforestation in an area of ​​very high biological diversity and, therefore, of pathogens”, says Fernandes-Ferreira.
Even so, considering other aspects that are not directly related to the environment was important for the research. One of the factors was the isolation of municipalities, where it was considered that the more the states had cities with low connections, the greater the probability of zoonoses outbreaks. This is because this isolation makes it difficult to access specialized health services.
The relevance of considering these other aspects can be seen in the comparison between Pará, which has medium risk, and Maranhão, with high risk.
Fernandes-Ferreira explains that, if only the presence of native forest and biodiversity were considered, Pará should have a greater risk than Maranhão due to deforestation in the Amazon.
It turns out that, when looking at other factors, the risk situation between the two states is reversed from what would be expected. “It is necessary to look at all economic and social contexts and potential routes of infection and contagion, which are aggravated by the economic and social context”, adds the biologist.
Ways to prevent further outbreaks
The researchers say that the study shows points of attention to stop the emergence of new outbreaks. Even so, it would be important to improve the data available in Brazil to measure risks in more detail, such as the chances of an outbreak at the level of Brazilian municipalities, says Winck.
The authors also state that stopping the spread of diseases is related to the main ways that pathogens are transmitted.
One of these means is the illegal hunting and marketing of these meats that may be infected. “Hunting is the main route of direct contact between humans and pathogens from wild mammals”, says Fernandes-Ferreira.
Another way is vectors, such as mosquitoes, which can spread zoonoses directly to humans. In this case, the greater the deforestation, the greater the exposure to these situations. In addition, domestic animals can be bridges between pathogens present in wild animals and humans.
All these circumstances are related to deforestation and human presence in areas of native fauna. Therefore, the researchers emphasize that environmental preservation is the most urgent point to prevent new outbreaks.
“The problem is the impacts on biodiversity areas. These areas need to be conserved. The recipe we showed is not something that can happen. It already happens. Yellow fever, dengue, chikungunya, Covid and malaria are diseases with this recipe. situations that already happen in Brazil. What we show is how much more it can happen, where and by what factors”, concludes Fernandes-Ferreira.
