Human and Animal Viruses

This chapter provides an overview of the human and animal viruses. Viruses held to a low number of passages in animals or cell cultures represent a viral population that is similar to that found in nature, and freezing these pools guards against genetic mutations that occur during subsequent passage. Aliquots of viral stocks frozen at a designated passage level can then be used for multiple and repeatable experiments with the same viral population. Furthermore, it is important that consistency should be maintained during the production of viral vaccines; new lots of final product are prepared with frozen viral seed stocks that consistently reproduce the desired immunogenic and attenuation characteristics. To better appreciate the requirements for freezing and freeze drying of human and animal viruses, some consideration is given to understanding the structural and functional organization of this diverse group of microorganisms. The classification of viruses is based on morphological and physiochemical properties. Thus, viruses are divided into those with DNA or RNA genomes and subdivided into families based on size and structural properties. Several methods for preservation of viruses are included in the chapter.