Varicella–zoster virus (VZV) is a herpesvirus and causes chickenpox with primary infection, a highly contagious disease characterized by widely spread vesicular eruptions and fever. The disease is endemic in the United States and most commonly affects children 5–8 years of age, although adults and younger children, including infants, may develop chickenpox. VZV infection in a pregnant woman may spread through the placenta to the fetus, causing congenital disease in the infant.
Although a primary infection results in immunity to subsequent chickenpox, the virus remains latent in the body. When it is reactivated, VZV causes shingles (herpes zoster). The incubation period is 10–24 days. Fever and painful localized vesicular eruptions of the skin along the distribution of the involved nerves are the most common clinical symptoms.
The sensitivity, specificity, and reproducibility of ELISA immunoassays are comparable to other serologic tests for antibody such as IFA, CF, and HAI. A positive IgG result, coupled with a positive IgM result, indicates a current infection with VZV.
Negative for varicella–zoster IgG or IgM antibodies by ELISA: nonimmune
Positive for varicella–zoster IgG antibody: indicates a current or previous infection; in the absence of current clinical symptoms, may indicate immunity
Positive for varicella–zoster IgM antibody; indicates a current or recent infection
Collect a 7-mL blood serum sample in a red-topped tube. Observe standard and airborne precautions. Label the specimen with the patient’s name, date, and test(s) ordered and place in a biohazard bag for transport to the laboratory.
Follow-up testing may be required.
When testing for IgG antibody, seroconversion between acute and convalescent sera is considered strong evidence of a current or recent infection. The recommended interval between an acute and convalescent sample is 10–14 days.
Whereas the presence of IgM antibody suggests a current or recent infection, low levels of IgM may occasionally persist for more than 12 months after infection or immunization.
Immunosuppressed patients in hospitals may contract severe nosocomial infections from others infected with VZV. Therefore, serologic screening of direct healthcare providers (e.g., primary providers, nurses) is necessary to avoid spread of infection.
Pretest Patient Care
Assess patient’s test knowledge. Explain test purpose and procedure. Advise pregnant women that VZV poses a high risk for congenital disease in the infant.
Follow guidelines in Chapter 1 for safe, effective, informed pretest care.
Posttest Patient Care
Review test results; report and record findings. Modify the nursing care plan as needed. Counsel the patient regarding abnormal findings; explain the need for possible follow-up testing and treatment. Inform patients who test positive for VZV IgG that they are naturally immune to chickenpox, but the virus can be reactivated and cause shingles at a later time.
Institute or maintain airborne and contact precautions for active VZV infection.
Follow guidelines in Chapter 1 for safe, effective, informed posttest care.