The appearance of chicken infectious anemia (CAV) infection in Israeli commercial chicken flocks [1, 2] led to the development of novel criteria for a more significant definition of virulence. Infection trials were conducted in experimentally-inoculated embryonated eggs and in inoculated and contact-infected one-day-old CAV-negative SPF chicks. The CAV embryo pathogenicity trial employed twelve CAV strains. For the first time we showed that CAV influences the growth rate of embryonated eggs and induces lesion in the embryos. Further, we analysed the kinetics of such influences by sampling groups of ten embryos from inoculated and from uninoculated embryonated eggs at two-day intervals. Both experiments revealed that CAV inoculated at embryonic day 7 induced pathological changes and retarded embryo growth. We concluded that CAV infections of embryonated eggs are potentially teratogenic. Two CAV isolates, #2 and #10, causing embryo pathogenicity, were selected for further biological characterization in one-day-old chickens, alongside with the CIA-1 strain of CAV. The infection trial was followed for 35 days, and we described the sequential pathological, virological and serological events. We revealed a systematic description of the horizontal CAV spread from inoculated to contact-infected chickens housed in the same isolator, and developed a new scoring system for assessing the severity of the histopathological lesions.