How Do Viruses Cause Different Diseases?

Excerpt

VIRUSES are capable of causing a wide variety of clinical illnesses.¹ Such illnesses vary from asymptomatic or mild infections, such as the common cold, to rapidly progressive fatal infections, such as rabies or herpes encephalitis. In addition to differing in the severity of illness, different viruses are associated with highly distinct patterns of illness. For example, the most common of all clinical illnesses are associated with infections of surface epithelial cells, either the respiratory epithelium of the tracheobronchial tree (as best illustrated by influenza) or gastrointestinal (GI) tract absorptive cells (as seen in the diarrheal illnesses caused by the human rotaviruses).² In both of these instances, the infection is usually limited to epithelial cells directly in contact with the primary portal of entry, the nose or the mouth. A second general pattern of infection is illustrated by a wide variety of viruses that, after entering through a primary