US Pharm. 2019;44(8):36-38.
Zika virus was discovered in 1947 in monkeys inhabiting Uganda’s Zika Forest, and the first outbreak was recorded in Micronesia in 2007, with patients showing symptoms of rash that appeared to be associated with the viral infection.1 In 2015, patients in Brazil with suspected Zika virus exhibited signs and symptoms of Guillain-Barré syndrome (GBS) and microcephaly.2,3 The World Health Organization notes that Zika virus is transmitted by a bite from infected Aedes mosquitoes (Aedes aegypti and Aedes albopictus).3 It can also be spread via sexual intercourse and perinatally.4 No vaccines are available to prevent infection, and there are no known treatment modalities.
Regions with a reported risk of Zika virus include Africa, Asia, the Caribbean, South America, and North America (United States and Mexico).5,6 Disease prevalence has been reported for Uganda, Indonesia, and North, South, and Central America.1,6,7 The largest number of symptomatic cases in the U.S. (recorded in 2016) was 41,409, with 12% of cases occurring in the 50 states and 78% in U.S. territories (Puerto Rico, American Samoa, and Virgin Islands). In 2018, 220 cases were reported inside the U.S. (32%) and its territories (67%); California had the largest number of cases (50%), followed by Florida with 25% of cases.
Clinical Signs, Symptoms, and Complications
Most patients with Zika virus are asymptomatic or have self-limiting mild symptoms resembling those for dengue and chikungunya viral infections.8 These symptoms, including fever, joint and muscle pain, headache, rash, and red eyes, can last for several days to weeks but are sufficiently mild that the patient may not seek medical care. The incubation period is approximately 3 to 14 days, and symptoms last 2 to 7 days.3,6,8 Zika virus can have potentially serious complications, such as GBS and microcephaly in newborns.2,3,9-11 Zika virus has been isolated in urine, blood or serum, vaginal fluids, and semen; its presence in amniotic fluid is being investigated.12
Zika virus testing should be performed in individuals who have traveled to high-risk countries, sexually active women whose partners travel to areas with high Zika risk, pregnant women with viral exposure or symptoms or who have abnormal fetal ultrasound findings, and all other persons with active Zika virus symptoms.6
Patients are screened based on recent travel history, presence of signs and symptoms, and test results. The simplest way to confirm the presence of Zika virus is through a blood or urine sample. The FDA approved the first Zika virus screening method—the cobas Zika test—in October 2017. This test, which uses qualitative nucleic acid to detect Zika virus RNA, was not intended for general use and may be performed only at designated blood-collection establishments that screen donated blood. The FDA has since authorized approximately 18 different nucleic acid testing–based assays via the Emergency Use Authorization.13
ZIKV Detect 2.0 IgM Capture ELISA
On May 23, 2019, the FDA authorized marketing of the ZIKV Detect 2.0 IgM Capture ELISA kit (FIGURE 1), a diagnostic test manufactured by InBios International, Inc.14 This enzyme-linked immunosorbent assay (ELISA) is the first diagnostic tool approved for detection of Zika virus antibodies in human serum. Recombinant viral antigen engineering enables specificity in recognizing immunoglobulin M (IgM) antibodies, which are an early immune-system response to Zika virus exposure. IgM targets envelope protein, one of three proteins the virus produces (the others being nonstructural protein and premembrane protein).15-17 ZIKV Detect 2.0 IgM Capture ELISA was developed specifically to identify IgM antibodies in human serum.15
The kit contains all materials needed for the test, including IgM test strips, ZIKV IgM-positive and -negative controls, recombinant ZIKV antigen, cross-reactive control antigen (CCA), normal cell antigen (NCA), secondary antibody, conjugate, liquid tetramethylbenzidine substrate, and acidic stop solution.15 If IgM antibodies resulting from Zika virus exposure are present in the serum sample, they form a complex with the kit’s ZIKV antigen, secondary antibody, and conjugate. If the serum contains no IgM, no complex is formed, resulting in a negative test. Results should be read within 30 minutes after the stop solution is added. The manufacturer recommends that the specifications for preparation, assay procedure, calculations, and quality control be followed strictly. Additional information may be found in the package insert or at https://inbios.com.
ZIKV Detect 2.0 IgM Capture ELISA is approved only for use in patients who have signs and symptoms of Zika virus infection or meet CDC criteria (e.g., residence in or travel to high-risk regions, exposure, pregnancy with or without symptoms of Zika infection, and confirmed positive results on the plaque reduction neutralization test [PRNT]).6
ZIKV Detect 2.0 IgM Capture ELISA is the first commercial serologic test for detecting the presence of Zika virus antibodies in the general population.15 Given this availability, it is conceivable that both the incidence of and surveillance for the Zika virus will be standardized, positive cases in the population will be reported, and treatment modalities will be developed.
Specificity and Sensitivity: ZIKV Detect 2.0 IgM Capture ELISA is specific for detecting antibodies that target Zika virus envelope proteins. Possible results are positive, presumptive Zika virus–positive, possible Zika virus–positive, nonnegative, ambiguous or equivocal, or Zika virus–negative based on the average absorbance OD450 (optical density at 450 nanometers) values obtained on the spectrophotometer. The lowest concentration of OD (225 IU/mL) is necessary for a presumptive Zika virus–positive result in 95% of replicates. These values are then calculated for the ZIKV antigen, CCA, and NCA. The ratios of ZIKV antigen/CCA and CCA/NCA are also calculated, and ambiguous results are retested.15 A negative result does not negate the presence of infection, and PRNT may be necessary for confirmation. PRNT may be performed in any patient (except those living in Puerto Rico) with a false-positive sample.6
Healthcare-Personnel Training: ZIKV Detect 2.0 IgM Capture ELISA availability will enable reporting of incidence rates and surveillance data. Personnel involved in administering the test and collecting data are responsible for reporting all results and other information related to the test. Other responsibilities include proper training, handling, and disposing of test specimens and used materials. The Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health published an Interim Guidance document containing information on Zika virus prevention to reduce exposure of occupational workers to the virus.18 ZIKV Detect 2.0 IgM Capture ELISA contains serum or plasma materials that are potentially hazardous and infectious despite being heat-inactivated. The manufacturer recommends that Clinical and Laboratory Standards Institute–approved guidelines be used to train personnel on handling and storage of the kit materials and that strict laboratory techniques and safety precautions be employed in collecting and handling specimens and in performing the test.15
Limitations: ZIKV Detect 2.0 IgM Capture ELISA has several limitations, but these should not deter healthcare professionals from using the test when indicated. The manufacturer recommends that the test results, whether positive or negative, be used in conjunction with clinical evidence of symptomatology, history of exposure or predispositions, and other laboratory results.15 The window of detectable antibodies is considered to start at day 4 of symptom onset and can extend as far as 84 days from symptom onset, and taking samples before the fourth day of exposure may result in a negative test. A negative result can also occur if the test is performed later, after the antibody (IgM) has declined to undetectable levels. The manufacturer does not recommend using this test on the blood or plasma of donors. Once specimens are collected, the test should be performed as soon as possible to avoid contamination and prolonged exposure of the serum specimen to room temperature. When storage is necessary, the specimen must be kept at –20°F or colder. Samples must be thawed at room temperature, and rethawing should not be done more than three times. There may be cross-reactivity with other viruses, such as dengue, chikungunya, and yellow fever, which may lead to false-positive Zika virus results.
Zika virus is transmitted primarily by one infected human to another following an Aedes mosquito bite. Other modes of transmission include blood transfusion, sexual intercourse, and mother-to-fetus. The most serious complications of Zika virus infection are GBS and microcephaly. Diagnosis of Zika virus infection has become easier since the FDA’s approval of the ZIKV Detect 2.0 IgM Capture ELISA kit.
1. Dick GW. Epidemiological notes on some viruses isolated in Uganda; Yellow fever, Rift Valley fever, Bwamba fever, West Nile, Mengo, Semliki forest, Bunyamwera, Ntaya, Uganda S and Zika viruses. Trans R Soc Trop Med Hyg. 1953;47:13-48.
2. European Centre for Disease Prevention and Control. Zika virus disease epidemic: potential association with microcephaly and Guillain-Barré syndrome (first update). http://ecdc.europa.eu/en/publications/Publications/rapid-risk-assessment-zika-virus-first-update-jan-2016.pdf. Accessed May 24, 2019.
3. World Health Organization. Zika virus. www.who.int/news-room/fact-sheets/detail/zika-virus. Accessed May 24, 2019.
4. Besnard M, Lastere S, Teissier A, et al. Evidence of perinatal transmission of Zika virus, French Polynesia, December 2013 and February 2014. Euro Surveill. 2014;19:20751.
5. FDA. Zika virus response updates from FDA. www.fda.gov/emergency-preparedness-and-response/mcm-issues/zika-virus-response-updates-fda#nat. Accessed May 24, 2019.
6. CDC. Zika virus. www.cdc.gov/zika. Accessed July 19, 2019.
7. Roth A, Mercier A, Lepers C, et al. Concurrent outbreaks of dengue, chikungunya and Zika virus infections—an unprecedented epidemic wave of mosquito-borne viruses in the Pacific 2012–2014. Euro Surveill. 2014;19:20929.
8. Petersen E, Wilson ME, Touch S, et al. Rapid spread of Zika virus in the Americas—implications for public health preparedness for mass gatherings at the 2016 Brazil Olympic games. Int J Infect Dis. 2016;44:11-15.
9. Mlakar J, Korva M, Tul N, et al. Zika virus associated with microcephaly. N Engl J Med. 2016;374:951-958.
10. Rice ME, Galang RR, Roth NM, et al. Vital Signs: Zika-associated birth defects and neurodevelopmental abnormalities possibly associated with congenital Zika virus infection—U.S. territories and freely associated states, 2018. MMWR Morb Mortal Wkly Rep. 2018;67:858-867.
11. Adebanjo T, Godfred-Cato S, Viens L, et al. Update: interim guidance for the diagnosis, evaluation, and management of infants with possible congenital Zika virus infection—United States, October 2017. MMWR Morb Mortal Wkly Rep. 2017;66:1089-1099.
12. Paz-Bailey G, Rosenberg ES, Doyle K, et al. Persistence of Zika virus in body fluids—final report. N Engl J Med. 2017;379:1234-1243.
13. FDA. Zika virus diagnostic development. www.fda.gov/emergency-preparedness-and-response/mcm-issues/zika-virus-diagnostic-development. Accessed July 19, 2019.
14. Mezher M. FDA clears new tests for chlamydia, gonorrhea, Zika virus and prosthetic joint infections. Regulatory Focus. www.raps.org/news-and-articles/news-articles/2019/5/fda-clears-new-tests-for-chlamydia-gonorrhea-zik. Accessed July 19, 2019.
15. InBios. ZIKV Detect™ IgM Capture ELISA instructions for use. http://inbios.com/wp-content/uploads/2017/04/900211-01-EUA-ZIKV-Detect-IgM-Capture-ELISA-Insert.pdf. Accessed July 19, 2019.
16. Sirohi D, Chen Z, Sun L, et al. The 3.8 Å resolution cryo-EM structure of Zika virus. Science. 2016;352:467-470.
17. Screaton G, Mongkolsapaya J, Yacoub S, Roberts C. New insights into the immunopathology and control of dengue virus infection. Nat Rev Immunol. 2015;15:745-759.
18. OSHA/NIOSH FactSheet. Interim guidance for protecting workers from occupational exposure to Zika virus. www.osha.gov/Publications/OSHA3855.pdf. Accessed July 19, 2019.
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