A virus cannot reproduce on its own. It has to get inside a cell and use the works in there.

What it means

This is why it is arguable whether a virus is alive. Outside a host it does nothing at all: no eating, no growing, no reacting, just a package of genetic material in a protein shell that can sit inert for years. Once inside a cell it hijacks the machinery already there and turns it to making copies. Antiviral drugs are hard to design for exactly that reason, since almost everything the virus uses belongs to the patient.

The claim comes from MedlinePlus.

Nearby in the collection

The facts either side of this one.

• NCBI Bookshelfmedium, 75 letters
• MedlinePlusmedium, 72 letters
• MedlinePlus · National Library of Medicinemedium, 70 letters
• NIAIDmedium, 77 letters

About as hard as this one

Scored closest to it by the model behind our guide to solving cryptograms.

• NCBI Bookshelfeasy, 75 letters
• NHGRIeasy, 77 letters
• Brain Research Bulletineasy, 74 letters
• NCBI Bookshelfeasy, 77 letters