How can a dead protein reproduce and infect?

Viruses are not technically alive, so they do not reproduce or infect in the same way that living organisms do. Viruses consist of genetic material enclosed within a protein coat. They can replicate only by infecting living cells and exploiting their cellular machinery.

Viruses are made up of either DNA or RNA, but not both.

To infect a cell, a virus first attaches to specific receptors on the cell surface. This attachment depends on the type of virus and the cell it targets. After attachment, the virus injects its genetic material (either DNA or RNA) into the cell's cytoplasm.

Once inside the cell, the viral genetic material is transcribed and translated by the host cell's machinery to produce new viral components, including proteins and more copies of the viral genome. These components then assemble into new, fully infectious viruses within the host cell. The cell may produce hundreds to thousands of new virus particles, which are then released by rupturing the cell membrane and can go on to infect other susceptible cells.

Therefore, viruses do not reproduce on their own but rely on living host cells to replicate and spread.