RESUMO
The means by which replication of viruses takes place is explained, as it helps in the understanding of how viruses spread in the blood and how antiretroviral drugs work. The most important viruses, from a health care workers point of view, are hepatitis B and C and human immunodefiency virus (HIV). Whether nuclear medicine has a role to play in the diagnosis of these viruses, and the oportunistic infections that go with them, is debatable. Several radiopharmaceuticals are extremely sensitive for infection and tumor imaging but lack specificity. Patients' treatment is often not based on the outcome of the investigation but rather on preset protocols. AIDS patients are put on prophylactic antibiotic treatment as protection against infections such as toxoplasmosis and pneumocystis carinii pneumonia and there is a poor prognosis for AIDS patients with tumors