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 d.MAC and

CMV retinitis), but the clinician should be aware that infections may occur at a higher than anticipated CD4 levels.

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HUMAN IMMUNODEFICI ENCY VIRUS

CLINICAL PRESENTATION

� History

All patients presenting to the ED with complaints of infections should be asked about their HN status, if they have

been tested, and about pertinent risk factors. Patients with

unknown HN status, significant risk factors, and symp ­

toms consistent with an opportunistic infection should be

assumed to be immunosuppressed. Patients with known

HN 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/!!L 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 fur 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/!!L suggests central nervous system

( CNS) infection (toxoplasmosis or cryptococcal meningi ­