2023-11-07 03:05:29
Home of the greatest biodiversity on the planet, the Amazon is also a time bomb for the appearance or resurgence of diseases with pandemic potential. This is because environmental degradation and landscape alteration are important factors in this process, which is aggravated during periods of extreme drought, such as the one currently affecting the region.
In the Amazon in particular, the paving of BR-319, which links Porto Velho to Manaus, is a major source of concern. The most conservative estimates predict that deforestation around the road could quadruple in the next 25 years, mainly due to land speculation. This is compounded by the fact that 90% of the area directly affected consists of virgin forest areas.
Deforestation is not a static situation, but rather a dynamic and unpredictable one, which causes the fragmentation of forests, increases the risk of fires and reduces the biodiversity of the affected areas. The association between human action in the Amazon – such as the paving of the BR-319 highway and the illegal exploitation of areas for mining –, climate change, disorganized migration and precarious social development creates a favorable environment for major diseases reappear.
Known diseases
This process can occur in different ways. The degradation of conserved areas, the diversion of rivers and extreme droughts, for example, cause water and food shortages. And this poses a direct threat of malnutritionwhich affects the health of local populations, leaving them more vulnerable to known diseases.
Lack of clean water and poor hygiene in drought conditions also increase the risk of diseases transmitted by contaminated water and food, such as cholera and hepatitis, and viruses that cause severe diarrhea, such as rotavirus. To make matters worse, the incidence of diseases associated with poor fish preservation, such as rhabdomyolysis (black urine disease) – which is not infectious –, also increases during extreme droughts.
Global warming is also a critical factor in this process, since it allows the presence of mosquitoes that transmit diseases such as malaria and dengue to expand. An increase of just a few degrees in the planet’s average temperature can allow these vectors to colonize areas that were previously inaccessible to them, since they require relatively high temperature and humidity conditions. In the regions where they are present, environmental degradation can increase or decrease rainfall periods, favoring floods and the maintenance of stagnant waters, and facilitating their proliferation.
It is not surprising that vector-borne diseases are classic cases of outbreaks due to environmental imbalance. The recent humanitarian crisis of the Yanomami, a tragedy caused by illegal mining, land grabbing and lack of access to health services, is a case in point. In addition to the contamination of water and the environment by mercury, mining activities have created a favorable environment for the reproduction and propagation of mosquito species of the Anopheles genus, transmitter of the protozoan that causes malaria.
This is because the excavation of ravines for the extraction of gold and minerals creates pools of water that act as artificial breeding grounds. Besides, mining activity The human population increases in these remote regions, facilitating the spread of malaria. In numerical terms, while between 2008-2012 around 20% of malaria cases occurred in Yanomami territory, between 2018-2022 almost 50% of the cases affected this population.
And new diseases
But without a doubt, infectious diseases, especially zoonotic ones (transmitted from animals to people), are the most worrying. While some pathogens (disease-causing agents such as viruses and bacteria) are capable of infecting one or a few host species, others are more widespread and can, if there is contact and opportunity, infect a wide variety of animals. This type of “jumping” from one host to another constantly occurs among animals in their natural habitat, for example, from bats to non-human primates, small rodents and other mammals. However, there is usually a balance in the circulation of these agents.
But when habitats are destroyed, for whatever reason (caused or not by man), local species migrate to more conserved areas in search of food and shelter. And this can occur in areas close to human settlements, promoting contact between wild animals and people.
Impossible to predict, but possible to monitor
Unfortunately, preventing zoonoses is not an easy task. Although we know that we are close to the limits of a crisis of no return, there is no effective method that can predict how, where or what the next emerging disease will be.
But it is possible to monitor it. To do this, we monitor the circulation of resistant viruses and bacteria in water samples, animals and vectors, as well as in humans. Sentinel animals such as bats, rodents and primates undergo next-generation sequencing technologies for the early detection of circulating agents that could pose a threat to human health.
However, it is still not enough. To be effective, surveillance must be constant and encompass local and national levels. Although Brazil has the capacity and the basic technical infrastructure to do so, few actions are actually put into practice. In addition to surveillance, we need investments in faster and more accurate diagnostic methods that can make a difference and help contain, if not the emergency, the spread of a possible new disease with pandemic potential like covid-19.
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