Subepithelial invasion and lymphatic spread. After penetrating the epithelium and its basement membrane, viruses are exposed to tissue macrophages and can enter the lymphatics, which form a net work beneath the skin and mucosal epithelium. Virus that enters the lymphatics spreads to the lymph nodes. In the lymph nodes may be engulfed by macrophages. Virions may be inactivated and processed by macrophages and dendritic cells so that an immune response is activated.
Some viruses however replicate in macrophages, dendritic cells and in lymphatic cells.
Some viruses may pass directly to the blood stream. In the blood there is always a constant movement of lymphocytes and macrophages, also cytokines and complement. Mention that localized infections result in inflammation, production of cytokines etc. Infection that spreads beyond the primary site is called disseminated. If many organs infected is a systemic infection.