For example, enteroviruses and herpes simplex can cause CPE in 1 to 2 days and destroy the cell monolayer in 3 days. NOTE Many viruses multiply in cells without causing obvious CPE, e.g. some members of Retroviridae, Arenaviridae, and Paramyxoviridae families. The growth of such viruses must be assayed by complicated methods, which will be discussed later. Many viruses can be propagated in embryonated chicken eggs but the method is now only used for influenza viruses. Laboratory Animals Experimental animal are obligatory for studying virus pathogenesis , which is the processes by which viruses can cause disease.
Mice are the most widely used experimental animal.
In recent years, a new technology involving insertion of the DNA of the whole or part of the virus genome, resulting in expression in somatic cells of virus mRNA and proteins has been developed. A modification of this technique allows the targeting of these genes to specific cells, e.g. hepatocytes, neurons, etc by using cell-specific promoters in the transgene construction. The best example is the creation of transgenic mice expressing Hepatitis B virus. Morphology i.e. symmetry of the capsid, presence or absence of an envelope, and dimensions of the virion and capsid. Virus family have latinized names that start with capital letters and end with viridae .