COVID 19, fusion with a host cell, SARS-Cov2. This scientific illustration represents the fusion of the coronavirus (in green) with a host cell (in purple). When the virus reaches the respiratory system by inhalation, left side of the drawing, it fuses with a host cell. It is thanks to its protein S (spicule), a viral surface protein that SARS Cov2 will cling to the membrane receptors of the host cell. Besides the zoom in the center the illustration shows this grip between SARS CoV2 and the membrane of the host cell on a sectional view. While on the right of the drawing, the virus is represented in section with all its proteins. A distinction is therefore made between proteins S (spicules, green and red), proteins E (envelope proteins in yellow), the membrane proteins constitute the thickness of the membrane of the virus (in green). This section delimits the center of the virus in which we distinguish the N protein (dark pink balls) which, together with the viral RNA, constitute the nucleocapsid (in pink). Strasbourg, Bas-Rhin, France.