Patterns of Respiratory Viral Replication
Virus may reach the respiratory tract by several different routes, including nose-hand-nose transmission and aerosol transmission; relative temperature and humidity, as well as crowding and exposure, influence the seasonality of may of the respiratory viruses.
As a primary barrier to infection with epithelial and mucosal surfaces, the respiratory tract is a primary site of viral replication for a large number of viruses. The categories below illustrate why more than a common cold, the flu, or even coronaviruses such as COVID-19 may be considered and tested during workup.
- Acute infection with replication confined to the mucosal surface; Coronavirus COVID-19 falls into this category.
⁃Paramyxoviruses (Parainfluenza 1,2,3; Respiratory Syncytial Virus, RSV); Orthomyxofviruses (Influenza [Flu] A, B, C); Coronaviruses; Picornaviruses (Rhinoviruses); Herpesvirus (Herpes Simplex, HSV)
- Persistent replication on the mucosal surface
⁃Herpesviruses (Epstein-Barr Virus, EBV); Adenoviruses; Papillomavirus
- Systemic replication after primary replication on the mucosal surface.
⁃Paramyxoviruses (Measles; Mumps); Herpesviruses (Varicella, HHV-3; Sixth Disease, HHV-6; Cytomegalovirus, CMV); Togaviruses (Rubella); Bunyaviruses; Arenaviruses; Parvovirus; Picornavirus (Poliovirus); Poxviruses; Reoviruses
Epithelial cells infected with respiratory viruses respond by producing a mediator, interleukin-6 (IL-6); these levels increase significantly between 48 and 72 hours of infection.