Many viruses, including WNV, cold viruses, and flu viruses, reproduce in the host for a short period of time before being destroyed by the host’s immune system. This production of new virus particles occurs during a period in which virus particles are present in the blood (viremia). If Russell, the blood donor in the case, had been infected with WNV, he could safely make future donations once the viremia had passed and his blood no longer contained virus particles. In contrast, a person infected with HIV can never give blood. Examine the life cycle of HIV and suggest a reason for this. (Note: An immune system response is usually initiated by recognition of “nonself” molecules on the surface of infected cells.)