What inhibits viruses from entering and attacking healthy cells?

Viruses are inhibited from entering and attacking healthy cells primarily by the host's immune system, which includes physical barriers like skin and mucous membranes, as well as immune responses involving antibodies and specialized cells. Additionally, many healthy cells possess receptors that can recognize and block viral entry, while antiviral proteins can interfere with viral replication. The presence of interferons, signaling proteins produced in response to viral infections, also plays a crucial role in enhancing the antiviral state of neighboring cells.