Coronavirus
Cell entry

Infection begins when the viral spike protein attaches to its complementary host cell receptor. After attachment, a protease of the host cell cleaves and activates the receptor-attached spike protein. Depending on the host cell protease available, cleavage and activation allows the virus to enter the host cell by endocytosis or direct fusion of the viral envelope with the host membrane.

Coronaviruses can enter cells by either fusing to their lipid envelope with the cell membrane on the cell surface or by internalization via endocytosis.
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