The emerging infectious human viral diseases have been a prime concern for public health since the last decade. Various new viruses or virulent strains of old viruses have emerged during this period. Appropriate knowledge of the viral pathogenesis is required to understand their emergence and possible therapies. Various factors are involved in the emergence of viruses and new human diseases. Some of these human diseases are zoonosis. Zoonosis can be defined as human diseases caused by animal pathogens, which that are transmitted to humans. The WHO has been continuously updating the prioritizing list for various infectious, and emerging viruses. In this chapter, we discussed some important emergent viral pathogens, such as Ebola virus, Crimean-Congo Haemorrhagic Fever virus, and Marburg virus, Hanta, Hendra, and SARS. Detailed understanding of the emergence, the modes of transmission and pathogenesis, and possible treatment plans are necessary to check the invasion and outbreak caused by these viruses.