How do viruses invade mucous surfaces?

Abstract

One can express this subject in terms of the ‘strategy’ that a virus ‘uses’ to survive by ensuring passage from host to host. Firstly, viruses are shed into the environment by a route and in sufficient quantities to ensure access to the mucosa of another host. In this connection spread may be more successful if symptoms are produced; if, for instance, an intestinal virus produces diarrhoea or a respiratory virus causes sneezing. The virus has next to survive exposure to adverse circumstances such as drying in the air or exposure to light in order to retain sufficient viability when it reaches the mucosa: very labile viruses, such as genital herpes, are usually transmitted by close contact of mucosa to mucosa. The mucosal secretions, and in some areas the ciliary apparatus, form a barrier to all particles, including viruses. However, viruses do traverse them and reach the plasma membrane of susceptible cells in which they then initiate infection. It is possible that viruses may be trapped by phagocytic cells and be carried by them through the mucosa.