What is influenza?
Influenza - infection symptoms
The symptoms of infection with the influenza virus are usually violent. Depending on the predominant location where the virus particles proliferate, respiratory tract symptoms such as runny nose, sore throat and cough will occur. Obviously, combinations of these symptoms are often encountered.
When numerous cells of the respiratory tract epithelium have been infected and have been damaged or destroyed, the image of the damage visible under the microscope is similar to that of burn wounds. This damage causes the occurrence of the abovementioned clinical symptoms well noticeable for the infected person.
Local symptoms occur shortly (after a few hours to a few days) after the infection. The patient with influenza reports also generalised symptoms: headache, muscle and joint pain, malaise, muscle weakness, and even mental depression, and above all high fever. Viruses themselves do not cause any generalised symptoms. Viruses are usually limited to respiratory tract and (usually) they do not circulate throughout the body. Immediately after the viral infection, the organism reacts by simple defence mechanisms to counteract viral replication: it produces antiviral substances, mainly interferons. Interferons circulating with the blood throughout the body cause the occurrence of general symptoms which may be considered unintended side effects of the natural defence reaction of the body.
Influenza is manifested similarly as flu-like disease (FLD). It is characterised by:
- Acute onset
- Local (i.e. respiratory tract) symptoms representing virus replication
- General symptoms caused by the body’s own defence mechanisms
