[The molecular diagnostics of viruses]

For many years data of cancer research indicated that viruses can cause cancer. Virus infections induce cancer by different mechanisms. To predict the significance of a viral DNA fragment in human cells we have to be aware of the changes the particular virus is able to induce there.However, no matter which mechanisms of viral carcinogenesis are utilized, generally other factors (environmental, chemical, immunodeficiency, etc.) are also needed to induce invasive cancer in human. Before the introduction of nucleic acid based detection technique virus identification was a long and cumbersome process. This has been eliminated by the invention of recombinant gene technology and polymerase chain reaction. Virus nucleic acid can be detected without amplification using Southern, Northern and in situ hybridization. Techniques for target (polymerase chain reaction)or signal (hybrid capture, tyramine) amplification improved the sensitivity of detection. In the meantime, for the successful use of the arsenal of new methods we have to consider the characteristic feature of molecular virus research. A major achievement of molecular virus detection is that it proved the pathological significance of viruses in human cancers even in those where this was not expected. Hopefully these informations will increase the effort for elimination of oncogene virus infections.