Diagnosis

Because HSV-1 recurring infections tend to have a milder course than those due to HSV-2, some doctors now regularly test all infected patients for HSV type. These tests may be specifically beneficial for women who are pregnant or wish to conceive and for the partners of such women. They have limitations, however. For example, it is not clear if these tests are highly accurate in children. They also give no information on the location or duration of the infection.

Immunologic tests using urine or saliva, which would be particularly useful for testing children, are under investigation.

Tests for HSV Encephalitis

Diagnosis of HSV encephalitis may require a number of tests.

Imaging Tests. Electroencephalography traces brain waves and can identify about 80% of cases. Computed tomography (CT) or magnetic resonance imaging (MRI) scans may be used to differentiate encephalitis from other conditions.

Brain Biopsy. Brain biopsy is the most reliable method of diagnosing HSV encephalitis, but it is also the most invasive and is generally performed only if the diagnosis is uncertain.

Polymerase Chain Reaction (PCR). The polymerase chain reaction (PCR) assay looks for tiny pieces of the DNA of the virus, and then replicates them millions of times until the virus is detectable. This test can identify specific strains of the virus and asymptomatic viral shedding. PCR identifies HSV in cerebrospinal fluid and gives a rapid diagnosis of HSV encephalitis in most cases, eliminating the need for biopsies. Sensitivity is almost equal to viral culture and results are also much quicker. (An automatic PCR assay -- the LightCycler -- provides results in 2 hours.)