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  A high index of suspicion is needed for the initial diagnosis of human immunodeficiency virus (HIV), particularly in the context of atypical presenting symptoms. Consider acute HIV in the patient who presents with a mononucleosis-like infection, but with negative monospot testing.

  
  
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  CD4 T-cell count is correlated with risk for opportunistic infection.

  
  
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  All patients with HIV and respiratory complaints, especially those with CD4 <200 cells/μL should be placed in negative pressure/airborne isolation until the diagnosis of tuberculosis can be excluded.

  
  
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  With appropriate care and proper management, people living with HIV can live a normal lifespan.

Human immunodeficiency virus (HIV) is a cytopathic retrovirus that attacks the CD4 T-lymphocytes in the immune system. Acquired immunodeficiency syndrome (AIDS) occurs when HIV-induced loss of CD4 cells and the resulting immunosuppression permit infection from opportunistic pathogens. AIDS is defined as a CD4 count <200/μL, a CD4 percentage <14%, or the presence of an AIDS-defining illness. AIDS-defining illnesses include Pnemocystis jiroveci pneumonia (PCP), Mycobacterium tuberculosis (TB), toxoplasmosis, cryptococcosis, cryptosporidiosis, esophageal candidiasis, disseminated Mycobacterium avium complex (dMAC), and cytomegalovirus (CMV), among others.

In the United States, approximately 1.2 million persons are infected with HIV, with up to 50,000 new cases every year. The estimated prevalence of HIV-positive patients seen in urban emergency departments (EDs) may be as high as 11.4%. Up to 20% of all HIV-positive persons in the United States are unaware of their HIV status.

Risk factors for HIV acquisition include sexual activity, injection drug use, blood transfusion (particularly before screening of the donor pool commenced in 1985), intrapartum/neonatal exposure to a mother with HIV, and occupational exposure (break of skin with contaminated sharps or blood/body fluid splashes onto mucous membranes/non-intact skin).

Acute retroviral syndrome (ARS) occurs in approximately 50% of acutely infected patients, approximately 2–4 weeks after exposure to HIV, and may clinically manifest as a flu-like or mononucleosis-like illness. Regardless of the presence or absence of ARS, most patients have a high viral load (>10⁶ copies/cm³) during this period, and negative serologic tests. Seroconversion typically occurs 2–6 weeks (though sometimes up to 6 months) after exposure. An immune response to the virus is then generated, and the viral load falls to a setpoint with a relatively stable CD4 count. This leads to a period of clinical latency (usually 2–10 years) during which CD4 T-cells are continually destroyed and regenerated, and viral replication continues. Ultimately, immune control is ineffective, and the CD4 count falls, leading to increased susceptibility to opportunistic (as well as other) infection. Some CD4 cutoffs are associated with increased risk of certain infections (<200 with PCP, <100 with histoplasmosis, <50 with dMAC and CMV retinitis), but the clinician should be aware that infections may occur at a higher than anticipated CD4 levels.

History

All patients presenting to the ED with complaints of infections should be asked about their HIV status, if they have been tested, and about pertinent risk factors. Patients with unknown HIV status, significant risk factors, and symptoms consistent with an opportunistic infection should be assumed to be immunosuppressed. Patients with known HIV should be asked about their latest CD4 count, viral load, medications (including prophylaxis), and history of any opportunistic infections or recent hospitalizations. Patients with counts >500/μL are at lower risk for opportunistic infections.

Some aspects of the history are particularly important for specific, symptomatic presentations in those who are infected with HIV.

Fever. Pulmonary and CNS infections are the chief causes of fever, but infections at these sites may occasionally present without localizing symptoms.

Respiratory complaints. Any pulmonary complaint should raise suspicion for pneumonia or TB. Patients should be asked about prior episodes of PCP or TB. They should also be questioned about the use of prophylactic medications (eg, trimethoprim-sulfamethoxazole) for PCP. The presence of oral candidiasis in a patient with shortness of breath suggests PCP.

Neurologic complaints. New or worsening headache with CD4 count <200/μL suggests central nervous system (CNS) infection (toxoplasmosis or cryptococcal meningitis) or primary CNS lymphoma. Painless visual loss occurs with CMV retinitis.

Gastrointestinal complaints. Difficulty swallowing occurs with candidal esophagitis, and failure to improve with fluconazole (Diflucan) suggests CMV or herpes esophagitis. Acute diarrhea may be caused by bacteria (eg, Salmonella), whereas chronic diarrhea may represent a parasitic (eg, Giardia, Cryptosporidium) or viral (eg, CMV) cause. Pancreatitis and kidney stones most often occur as a result of antiretroviral therapy.

Physical Examination

A comprehensive physical examination may not only help provide a general picture of the overall health of the patient, it can also help identify the source for any acute presenting complaint. Some key systems to examine include:

Vital signs. History of fever at home requires a work-up, even if the patient is afebrile in the ED. Tachypnea and hypoxia suggest PCP.

General appearance. Assess for respiratory distress. Wasting, dehydration, and parietal hair loss are common in patients with advanced AIDS.

Head and neck. Assess visual acuity and perform funduscopic examination for possible CMV retinitis (“ketchup and mayo” retinal findings). Perform oral examination for candidiasis (thrush) and oral hairy leukoplakia (Figure 37-1). Assess the neck for lymphadenopathy or meningismus.

Pulmonary. Auscultate for rales, rhonchi, or wheezes; however, many patients with PCP will have normal breath sounds.

Cardiovascular. Listen for new murmurs, suggesting endocarditis, especially in the IV drug user.