Although many viral infections cause severe illness and even death over a period of days to weeks, such infections typically induce immune responses involving both neutralizing antibodies that prevent further viral replication and
cytotoxic T lymphocytes that recognize and eliminate infected cells that produce progeny virus. Such responses ultimately control and eliminate the virus effectively. Immunologic memory is established, and the person is left with protective immunity against subsequent infection with the same virus; this immunity is usually complete and long lasting.