For centuries the healers were aware of the diseases that we now know to be caused by viruses, but not the triggering factor. It was thought that the diseases were caused by a "poison". Until the 19th century, scientists were unable to isolate and determine the crucial substances.
The discovery of viruses
Then the researchers Friedrich Löffler and Paul Frosch made an interesting discovery as part of their research on foot-and-mouth disease in cattle: no matter how much they diluted the infectious fluid from the vesicles of the sick animals - the disease always appeared with the same intensity. They concluded that the so-called poison could multiply itself in some form. Derived from the original classification as "poison", this mysterious, disease-causing substance has been called "virus" in medicine, the Latin word for "poison" or "mucus".
1892: The first virus is identified
Among the light microscopes available in the 19th century, viruses could not be detected; they obviously had to be extremely small. With the proof that viruses are much smaller than bacteria, the Russian Dimitri Ivanovsky baffled the experts in 1892. He used filter filters to extract extracts from tobacco plants that were affected by the so-called "mosaic disease." The pores were smaller than 0.2 micrometers (one micrometer is one millionth of a meter), so bacteria in any case stuck in it However, Ivanovsky was able to infect other tobacco plants with bacteria-purified extract.
Findings: The viruses had to be smaller than 0.2 microns.
The tobacco mosaic virus deserves the dubious honor of being identified as the first virus. In the coming years, further discoveries followed in rapid succession. Among other things, the pathogens of foot-and-mouth disease, yellow fever and rabies were isolated. At the beginning of the twentieth century, the scientists first focused on the study of polio, which was becoming very widespread at the time. Thanks to the development of a vaccine, it was later, in the 1950s, contained and eventually eradicated. Because of the devastating effects of the Spanish flu (influenza) of 1918 also intensive research work was carried out.
1933: Influenza viruses are identified for the first time
About 20 years later: rhinoviruses that cause colds (flu infections) The development of the electron microscope by Ernst Ruska in 1940 made it possible to actually see viruses. From this point on, groundbreaking developments were found in all virus research, laying the foundation for modern molecular biology. These new techniques are being refined and improved on a daily basis by researchers worldwide. Today, the genetic information of a newly emerged virus type can be decrypted within a very short time.
Further information on viruses
We now know that viruses are particularly small, very simple infectious agents that invade the cells of an organism in order to multiply there with the help of the infected organism.
Viruses are between ten and 400 nanometers in size (one nanometer is one billionth of a meter). They consist of nucleic acid containing the genetic information of the virus and surrounding proteins. They do not have their own metabolism and are among the parasites.
Viruses are divided into different groups. These do not result from the diseases they cause, but according to the three criteria:
- Type of genetic information: RNA or DNA
- the symmetry principle, which follows the structure of the hollow body proteins surrounding the genetic information and
- the presence of an envelope membrane
Non-enveloped viruses, which include the cold-triggering rhinoviruses, have the characteristic of being very "environmentally stable". This means that, for example, they can not be killed by dehydration. Frequent hand washing in the annual cold season only serves to flush away the cold viruses, but can not destroy them. Controversial among scientists is whether viruses are living things or organic substances. A significant feature that defines "living things" is the ability to autonomously multiply.
However, viruses need host cells to multiply. For their classification as living beings speaks that they are able to multiply, to pass on their genetic material and to grow. However, they will need the help of the host cell that infected them. This provides the viruses with their mechanisms for propagation and ensures that the number of viruses in the host cell increases.