Shingles and Chickenpox (Varicella-Zoster Virus)

Description

Alternative Names

Diagnosis

Both chickenpox (varicella) and shingles (zoster) can usually be diagnosed using symptoms alone. If a diagnosis is still unclear after a physical examination, then diagnostic tests may be required.

Ruling Out Other Disorders

Either variation of the virus may be confused with other disorders.

Ruling out Disorders that Resemble Chickenpox. Chickenpox, particularly in early stages, may be confused with herpes simplex (the disorder more commonly referred to as "herpes"), or impetigo, insect bites, and scabies.

Ruling out Disorders that Resemble Shingles. The early prodrome stage of shingles can cause severe pain on one side of the lower back, chest, or abdomen before the rash appears. It therefore may be mistaken for disorders, such as gallstones, that cause acute pain in internal organs.

In the active rash stage, shingles may be confused with herpes simplex, particularly in young adults and if the blisters occur on the buttocks or around the mouth. Herpes simplex, however, does not usually generate chronic pain.

A diagnosis may be difficult if herpes zoster takes a non-typical course, such as with Bell's palsy or Ramsay Hunt syndrome in the face, or if it affects the eye, or causes fever and delirium.

Test to Identify the Virus

In most cases of chickenpox and shingles, the symptoms alone are sufficient to make a diagnosis. In some patients, such as those who are immunosuppressed, if the symptoms are not straightforward the physician performs one or more additional tests to detect the virus itself. They are usually performed to distinguish between varicella-zoster and herpes simplex viruses.

Virus Culture. A viral culture uses specimens taken from the blister, fluid in the blister, or sometimes spinal fluid. They are sent to a laboratory where it takes between one and 14 days to detect the virus in the preparation made from the specimen. It is also sometimes used in vaccinated patients to determine if a varicella-like infection is caused by a natural virus or by the vaccine. This test is useful, but it is sometimes difficult to recover the virus from the samples.

Immunofluorescence Assay. Immunofluorescence is a diagnostic technique used to identify antibodies to a specific virus. In the case of herpes zoster, the technique uses ultraviolet rays applied to a preparation composed of cells taken from the zoster blisters. The specific characteristics of the light as seen through a microscope will identify the presence of the antibodies. This test is less expensive than a culture, more accurate, and results are faster.

Polymerase Chain Reaction (PCR). Polymerase chain reaction (PCR) techniques use a piece of the DNA of the virus, which is then replicated millions of times until the virus is detectable. This technique is expensive but is useful for unusual cases, such as identifying infection in the central nervous system.