Viruses can cause a large number of different diseases. One can discriminate two basic classes of viruses: DNA and RNA viruses. The group of DNA viruses contains, for example, the family of herpes viruses like the Epstein-Barr-Virus (ERV) and the smallpox virus (also known as variola). The class of RNA viruses contains the family of human retroviruses HIV (human immunodeficiency virus) or the measles and influenza viruses. Members of both classes represent major health risks for humankind. In contrast to bacterial infections, which usually can easily been treated with antibiotics, no specific and successful treatment regimen exists for most viral infections. In most cases, the early verification of the presence of a viral infection is extremely difficult and usually only recognizable indirectly through the detection of a specific anti-viral immune response. However, latter one takes about a week to become measurable. The immune system is mostly turned adrift due to the fact that no effective treatment options exist as it is exemplified in the case of ERV, a viral infection that can cause infectious mononucleosis (Pfeiffer glandular fever). Additionally, the function of the immune system can only be supported by using established medication.