COVID- 19 is highly infectious disease where the first infected case reported in Wuhan city-China, then it was spread worldwide. The causative agent belongs to novel enveloped single linear positive-sense stranded RNA Coronavirus, which is also called SARS-CoV-2 and has an affinity to lung cells. The genetic analysis of SARS-CoV-2 suggested that this novehtm hgn l strain may be developed from the animal. origin by recombination between a bat SARS-like CoV and a coronavirus of unknown origin. The ability of rapid spread of SARS-CoV-2 virus from person to other is similar or even more than to other human viruses like influenza or plague leadding to be announced as a pandemic by WHO in 2020. The mortality rate in SARS-CoV-2 increased day by day and this led the scientists to search ways to control the virus. Most of the deaths in aged patients may be due to immune response complications where 70% of patients showed lymphopenia. This review, provided some details about structure, pathogenicity and immune response against SARS-CoV-2. The facts in this review lead to suggest that in most cases the death in SARS-CoV-2 may occur via loss of systemic inflammatory response control which leading to lung injury followed by pneumonia, acute respiratory distress syndrome (ARDS) and respiratory failure, hence the death especially in old patients. In concluding the early effective control of both innate and adaptive immunity may be the critical. key factor in protection against SARS-CoV-2.