Viruses depend<span> on </span>the<span> host cells that they infect to</span>reproduce<span>. When found outside of host cells, </span>viruses<span>exist as </span>a<span> protein coat or capsid, sometimes enclosed within </span>a<span> membrane. </span>The<span> capsid encloses either DNA or RNA which codes for </span>the virus<span> elements.</span>
