While Ebola has caused about 13,000 deaths since 1976, influenza accounts for 400,000 fatalities worldwide every year. Nevertheless, we should not lose sight of the immense progress that research has made in the fight against epidemics caused by viruses: Thanks to comprehensive vaccination campaigns, smallpox was finally eradicated in 1977, Kräusslich continued; poliovirus, the pathogen responsible for polio, is now found in only three countries in the world; and chronic hepatitis has been curable for the vast majority of patients since 2014. With appropriate medical treatment, AIDS is likewise no longer a death sentence.

In total, there are an estimated ten million times more viruses in the oceans than there are stars in the universe. And even the fundamental question of whether or not a virus is a living being can be answered in different ways, said Kräusslich. One thing is for certain: A virus comprises some 7,500 building blocks packed into a protein shell. It has a very simple blueprint, which we can regard as a biochemical compound at the interface between animate and inanimate matter. Without a host, the virus is nothing, with no function – but as soon as it encounters a suitable organism, it comes into action as an incredibly efficient reproduction machine, a radically “selfish genome”.

According to Kräusslich there is hardly any habitat on earth, no matter how extreme, that is not already colonized by viruses. They can be found not only on our skin, under the rose bush in the garden or beneath the next street lamp, but also in the deep sea, in acidic springs at a temperature of 80 degrees, in salt mines, and at depths of up to two kilometers below the earth's surface. It is thus important to recognize that viruses are not only potential pathogens, but also a basic constituent of ourselves as human beings.

Virus research will become increasingly important for medicine in the coming years. Despite numerous initial failures and setbacks in research, Kräusslich continued, some very promising new therapeutic approaches have now been developed: Viruses have proven to be ideal vehicles for introducing genetic information, such as therapeutic genes, into diseased cells. This has already made it possible to cure highly specific blood diseases in some patients. In future, virus therapies are likely to open up new opportunities for healing in the field of tumor medicine as well. The viruses could be introduced into cancer cells, for example, which they then strategically induce to self-destruct. “We still don’t understand many of these principles in detail, but in scientific terms we have now definitely reached a point from which we can open up completely new horizons,” Kräusslich concluded.