In the Emergency Department, patients present with diverse infectious diseases. Some diseases require a keen eye from the clinician to diagnose and prevent transmission and progression. HIV and TB are two conditions that are easily overlooked in the ED, yet are the two deadliest infectious diseases in the world. The HIV/AIDS epidemic has been a challenge to the United States health system since the 1980s and continues to represent major health and economic burden. TB cases in the US had been down trending in the 1950s, but since 1985 cases began to rise in urban areas where large communities of immigrants are present. The HIV and TB pandemics are largely intertwined because TB is a major cause of death in HIV patients. Most cases in the US are concentrated in urban areas of low income. Individuals of color, those experiencing homelessness, engaging in high-risk sexual behavior, and those with substance use disorder are the most likely to be affected. Advances in therapeutics as well as the development of screening modalities have made significant progress. The Emergency Department is the major point of contact for diagnosis and linkage to long-term care.

Key Learning Points

1. 1. There are four stages of human immunodeficiency virus (HIV) infection: primary HIV infection with a CD4 count of >500, chronic asymptomatic infection with a CD4 count of >350, symptomatic infections with a CD4 count of <350 and acquired immune deficiency syndrome (AIDS) accompanied by a CD4 count of <200.

2. 2. CD4 T-helper cell lymphocytes are responsible for both adaptive and cell-based immunity, and are active against both infectious disease and neoplasms.

3. 3. There are 27 AIDS-defining clinical conditions specified by the Centers for Disease Control and Prevention.

4. 4. Recent evidence suggests improved outcomes for intensive care patients treated with highly active anti-retroviral therapy (HAART).

5. 5. Intensive care patients not already treated with HAART, with a low CD4 count and an opportunistic infection, are at high risk of immune reconstitution inflammatory syndrome.