Pathogenesis of Viruses
An indicated before, viruses cause a number of infectious human diseases from minor ailments like common cold, to fatal disease, like yellow fever, rabies, cancer , AIDS, etc. Likewise, certain viral disease are sporadic some are endemic some are pandemic.
How viruses reach into our bodies
Different types of viruses reach into our bodies by different routes Respiratory tract is the most important route, Viruses of influenza, common cold measles, and smallpox mumps.etc. Enter into our bodies through this route with inhales air .Next to respiratory tract, the alimentary tract offers on important routed, viruses of polio. Polio, gastroenteritis, hepatitis etc. Enter through this route with food and drinks, Some viruses enter through skin abrasions insect bites viruses of dengue yellow fever encephalitis etc. Animal's bites or hypodermic needles (HIV) virus of hepatitis B etc
Spread of viruses in our body
Most viruses do not cause diseases immediately after their entrance into our bodies. First these undergo an incubation period of a few days dengue yellow fever etc, to several year during which these multiply in tissues lymphoid tissues, but in connective tissues, muscles. Verves, etc, in certain case which is associated with routes of entrance but are not the actual sites of infection. After multiply in these tissues the viruses spread in the body reach their target sots mostly through blood, or through central nervous system in some case.