If the habitat of animals is increasingly restricted, the risk of zoonoses – diseases between humans and animals – increases. An example of this is dengue fever. A virologist warns that this could now also spread in Germany.
Dengue fever, HIV and also Covid-19 – according to the Mainz virologist Bodo Plachter, the increase in viral diseases is a result of human misconduct towards the natural environment.
As Plachter says, with man-made global warming, diseases are to be expected in Central Europe that were previously limited to the tropics. “We will therefore very likely experience that dengue fever, for example, will also spread to us,” says the scientist.
Dengue fever is a high fever viral disease that is transmitted to humans by mosquitoes. According to the Tropical Institute, dengue is the most common mosquito-borne viral disease in the world. In this country, the disease primarily occurs in travelers who have traveled from countries such as Southeast Asia or South and Central America.
Typical contagion countries are Thailand, India, Indonesia or Brazil. In the meantime, infections in countries in southern Europe are also possible. The first infections were detected in travelers to southern France and Croatia in 2010. Even in the German summer, the mosquitoes can survive. The number of diseases in this country is also steadily increasing:
The problem: Normally, certain mosquito species die out in our latitudes in winter. With global warming, however, it can be expected that those who have not been able to survive the German winter will also survive, explains Plachter. This also applies to the dengue virus, which is transmitted by the Aedes mosquito – also known as the Asian tiger mosquito.
Thanks to the increased temperatures, the mosquito has the opportunity to spread further and further. It mainly occurs in urban areas. The female mosquitoes lay their eggs near small accumulations of water – for example in buckets, old tires, flower pots or rain barrels. Infected female mosquitoes transmit the dengue virus directly to their brood.
According to Plachter, the danger posed by viruses varies. “Viruses don’t want to make us sick,” emphasizes the scientist. “Their only goal is reproduction and – as is associated with this everywhere in nature – the preservation of their own species.”
A dengue infection is usually accompanied by a high fever and severe headache, muscle, bone and limb pain – hence the name “breakbone fever”. After a sudden rise in fever and subsequent reduction in fever, the temperature may rise again after a day or two.
A large-scale skin rash then often occurs, which may affect the entire body – but not the face. Small hemorrhages in the skin and mucous membranes are also possible. After being bitten by an infected mosquito, the symptoms usually appear after three to 14 days.
The typical symptoms are:
Those affected usually recover within a few days. If the course is mild, the symptoms last a maximum of three days. However, dengue fever can also lead to serious complications and even death.
Complications can occur with so-called hemorrhagic dengue fever (DHF) and dengue shock syndrome (DSS) – primarily in children. These are expressed as follows:
An infection with the dengue virus is usually detected via the blood through the detection of the pathogen and antibodies specifically directed against dengue viruses. Treatment has so far been limited to relieving the symptoms. There is also no vaccine against the virus yet.
According to Prachter, in addition to the dengue virus, the spread of the corona virus is also one of the “man-made disasters”. “Sars-CoV-2 was only able to spread so rapidly because we are penetrating deeper and deeper into areas where animals live that humans have hardly come into contact with before.” Many scientists think it is likely that it is Covid -19 is a zoonosis – an infectious disease that can be transmitted in both directions between animals and humans.
As the scientist explains, the main reason for the pandemic is the close contact with the animals: “If the living space for animals is further and further restricted, people increasingly come into contact with the pathogens that occur in them.” He cites chimpanzees as an example and gorillas are precursors to HIV. “Viruses that are transmitted to humans can adapt to this new host through mutations.”
“We are penetrating further and further into natural areas,” says Plachter. “The animals that live there are pushed out and then come to our cities like wild boar and fox.”
