The influenza viruses of the family Orthomyxoviridae are enveloped RNA viruses with a single-stranded RNA. A distinction is made between the four types of influenza A (FLUAV), B (FLUBV), C (FLUCV) and D (FLUDV). Influenza type C and type D viruses are not of great relevance in diagnostics. Type C leads, if at all, to mild diseases, while type D is not known to affect humans. Human influenza viruses are replicated in the respiratory tract of an infected individual, where they trigger an acute infection of the respiratory tract, the “real” flu or influenza.
Influenza must not be confused with a cold or “flu-like infection”, these are caused by other viruses, for example the Human Respiratory Syndytial Virus (HRSV or RSV, English: Human orthopneumovirus), Parainfluenza viruses, Rhino viruses (the “classic cold viruses”), Corona viruses (approx. 1/3 of all cases), adenoviruses (most common cold pathogen), enteroviruses (“summer flu”) or mastadeno viruses.
In Germany, waves of influenza occur in the winter months with varying degrees of spread and severity. In Deutschland kommt es in den Wintermonaten zu Grippewellen mit unterschiedlicher Ausbreitung und Schwere. Influenza viruses constantly mutate and thus form new variants. Due to these changes, it is possible that patients suffer from flu several times.