Viruses are difficult targets for chemotherapy because they replicate only within host cells, mainly utilizing many of the host cell's biosynthetic processes. It is becoming increasingly apparent, however, that each virus may have a few specific steps of replication that may be used as targets for highly selective, carefully aimed chemotherapeutic agents. Therefore, proper use of such drugs requires a thorough knowledge of the suitable targets, based on a correct diagnosis and a precise understanding of the replicative mechanisms for the offending virus. Knowledge of the pathogenetic mechanisms by which virus enters, spreads within, and exits from the body also is critical for correct diagnosis and treatment of disease and for prevention of spread in the environment. Many successful vaccines have been based on knowledge of pathogenesis and immune defenses.
Comparable considerations govern treatment with interferon.
Clearly, viral infections are among the most difficult and demanding problems a physician must face. Unfortunately, some of these problems still lack satisfactory solutions, although tremendous progress has been made during the last several decades. Many aspects of medical virology are now understood, others are being clarified gradually, and many more are still obscure. Knowledge of the properties of viruses and the relationships they establish with their hosts is crucial to successful investigation and clinical management of their pathologic processes. Our plan for conveying this knowledge is to present, first, concepts of viral structure, and then relate them to principles of viral multiplication.