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Zika and Other Emerging Viruses Transmitted by Aedes Mosquitos

This is an outdated version of this FAQ. It was effective 02/09/2016 to 05/03/2016.

The current version is available here.

Test Code(s):

 

Dengue: 18928, 92942, 93192, 37580, 37579, 93256

Chikungunya: 40066, 70188

Zika: contact your local health department or the CDC

Question 1. What is the Zika virus?

Zika is a virus transmitted by Aedes mosquitoes, found primarily in tropical locations. The same mosquitoes can also spread the dengue and chikungunya viruses. All 3 viruses can have overlapping clinical symptoms and may be found in the same geographic locations.

Question 2. Where has the Zika virus been found?

Outbreaks have occurred in parts of Africa, Southeast Asia, and the Pacific Islands. In May 2015, Brazil reported the first outbreak of Zika virus infection in the Americas. As of January 2016, the Zika virus has been reported in 19 countries or territories in the Americas.1

Zika virus is not currently believed to be transmitted by mosquitoes in the continental United States, but has been reported in Puerto Rico. However, recent cases of Zika infection have been reported in U.S. travelers who returned from Central and South America and the Caribbean. The number of individuals diagnosed will likely increase as the outbreak grows.

Map of locations with documented local transmission of Zika virus infection

Source: http://www.cdc.gov/mmwr/volumes/65/wr/mm6503e1.htm

Question 3. Who is at risk for Zika virus infection?

Anyone living in or traveling to an endemic area is at risk if bitten by a mosquito. In addition, persons in areas where the Aedes mosquitoes are found may also be at risk as the virus expands its geographic range. Aedes mosquitoes have been found in some areas of the southern United States, including Southern California, but local transmission at this point has not been seen.

Question 4. What are the signs and symptoms of Zika virus infection?

Most (80%) of the people infected with Zika virus are asymptomatic.1 When symptoms do occur, they are usually mild and may include fever, maculopapular rash, arthralgia, or nonpurulent conjunctivitis. Symptoms typically last from several days to 1 week. Based on information from previous outbreaks, severe disease requiring hospitalization is uncommon, and fatalities are rare.

The virus may be associated with Guillain-Barré syndrome, a rare paralytic syndrome that sometimes occurs after certain infections. Birth of an infant with microcephaly, a congenital abnormality, may be associated with Zika infection in pregnant women (see below). The association with microcephaly has not been seen in other outbreaks of Zika infection nor in other viral illnesses transmitted by the Aedes mosquito.

Question 5What other modes of transmission are there?

In addition to mosquito-to-human transmission, Zika virus infection can be transmitted from mother to child during pregnancy, resulting in congenital infection. The virus can also be spread via sexual activity (rare), blood transfusion, and laboratory exposure. There is a theoretical concern that transmission could occur through organ or tissue transplantation. Although Zika virus RNA has been detected in breast milk, transmission through breastfeeding has not been documented. There are no current recommendations in the United States to avoid breastfeeding; however, the CDC recommends pregnant women abstain from sex or use condoms for all sexual activity if their male sexual partner has traveled to, or lives in, an area with active Zika virus transmission. This recommendation should be followed for the duration of the pregnancy.2

Question 6What is the potential risk of Zika infection during pregnancy?

Zika virus can be transmitted from a woman to her baby during pregnancy or around the time of birth. It is currently not known how often this occurs. In contrast to previous Zika outbreaks, there has been a marked increase in the number of infants born with microcephaly in Brazil. Although it is unknown how many of these cases are related to Zika infection, at least some of the infants are known to be infected. There have also been some cases of confirmed Zika RNA in fetal loss specimens; however, it is unknown whether Zika infection increases the risk of fetal loss.

Per the Centers for Disease Control and Prevention (CDC), the increased occurrence of microcephaly in Zika virus-affected areas is suggestive of a possible association. Additional studies are warranted to confirm the association and to understand any other adverse pregnancy outcomes associated with Zika virus infection.

Because of this potential association, and with an abundance of caution, the CDC has issued a travel alert (Level 2, Practice Enhanced Precautions) for people traveling to certain regions and countries where Zika virus transmission is ongoing. The alert includes travel to multiple countries in the Caribbean, South America, Central America, Mexico, Samoa, and Cape Verde. As the outbreak is evolving quickly, please refer to the CDC for updated travel notices (http://wwwnc.cdc.gov/travel/notices).

Women who are pregnant, or are planning to become pregnant, are advised to postpone travel to affected areas if possible. Some countries are recommending that women try to postpone pregnancy until the outbreak is contained. Pregnant women in Zika virus-affected areas should protect themselves from mosquito bites by using air conditioning and screens to keep mosquitoes outdoors, using bed nets if unable to keep mosquitoes outdoors, wearing long sleeves and pants, using permethrin-treated clothing and gear and insect repellents. Pregnant and lactating women can use all U.S. Environmental Protection Agency (EPA)-registered insect repellents according to the product label. For additional information about pregnancy and the Zika virus, refer to these 2 Web sites:

Question 7. Who should be tested for a Zika infection?

Zika testing should be considered for symptomatic people who have been in an affected region within the 2 weeks before start of symptoms (incubation is 3 to 12 days after exposure). In addition, the CDC recommends testing pregnant women who have traveled to an affected region and who have 2 or more symptoms consistent with Zika infection or an ultrasound which shows fetal microcephaly or intracranial calcifications. The CDC also recommends testing asymptomatic pregnant women if they have traveled to areas with ongoing Zika virus transmission. Serologic testing can be offered 2 to 12 weeks after return from travel.

Criteria for evaluating and testing infants can be found in the CDC interim guidelines (see Question 10).

Question 8. Which tests are recommended for diagnosing Zika virus infection?

The recommended tests include Zika viral RNA and/or antibody tests. It is further recommended that all persons suspected of having Zika infection be tested for chikungunya and dengue infections too. The symptoms overlap, and the viruses are transmitted in the same regions, by the same mosquito vector.

Question 9. How can I access these tests?

Currently, Quest Diagnostics and other commercial laboratories do not offer Zika viral RNA PCR or Zika antibody testing. Zika virus testing will need to be coordinated with your local Public Health Department or the CDC. Some state public health laboratories can do the testing.

Chikungunya and dengue virus testing is available through Quest and is performed at Focus Diagnostics, a Quest subsidiary. As viremia occurs early but is short-lived, the following tests are available for the first week of symptoms:

  • Chikungunya Virus RNA, Qualitative Real-Time PCR (test code 40066)
  • Dengue Virus RNA, Qualitative Real-Time PCR (test code 18928)
  • Dengue Virus NS1 Antigen (test code 92942)
  • Dengue Fever Antibodies (IgG, IgM) and NS1 Antigen Panel (test code 93192)

Antibody or antigen tests are available after the first week of symptoms:

  • Chikungunya Antibodies (IgG, IgM) with Reflex to Titer (test code 70188)
  • Dengue Fever Antibody (IgM) (test code 37580)
  • Dengue Fever Antibody (IgG) (test code 37579)
  • Dengue Fever Antibodies (IgG, IgM) (test code 93256)

Chikungunya IgM antibodies usually develop first, followed by IgG antibodies, which lag behind by 1 to 4 days. Acute-phase serum specimens should ideally be collected after the first week of symptom onset. Convalescent-phase specimens, if tested, should be collected 10 to 14 days later. Specimens with a positive result(s) are serially diluted and tested to determine the class-specific immunoglobulin titer.

There can be significant cross-reactivity with dengue fever antibodies and other flaviviruses such as Zika, West Nile, and yellow fever. Acute-phase serum specimens should ideally be collected after the first week of symptom onset. Convalescent-phase specimens, if tested, should be collected 10 to 14 days later.

Dengue NS1 antigen is found in serum during the acute phase (days 1-9 after onset of symptoms). NS1 antigen may be positive when RNA and/or IgM assays are negative. Thus, NS1 antigen detection can serve as an effective bridge between dengue RNA detection (usually negative by day 5) and dengue IgM detection (may not be positive until day 6). There is no potential cross-reactivity of the NS1 antigen with other flaviviruses, unlike with antibody testing. For more information about the Dengue NS1 Antigen test, refer to our FAQ.

Question 10Where can I get more information?

Additional information about Chikungunya virus and the available tests can be found at: QuestDiagnostics.com/TestCenter/TestGuide.Action?dc=CF_Chikungunya.

For more information about testing for all 3 viruses, refer to the CDC memorandum (January 13, 2016) “Updated Diagnostic Testing for Zika, Chikungunya, and Dengue Viruses in the US Public Health Laboratories” at http://www.cdc.gov/zika/pdfs/denvchikvzikv-testing-algorithm.pdf.

Information and guidelines concerning the Zika virus are rapidly evolving. For the latest updates, see the “CDC Guidelines for Health Care Providers” at http://www.cdc.gov/zika/hc-providers/index.html.

 

References

  1. Hennessey M, Fischer M, Staples JE. Zika virus spreads to new areas—region of the Americas, May 2015-January 2016. MMWR Morb Mortal Wkly Rep. 2016;65:55–58. DOI: http://dx.doi.org/10.15585/mmwr.mm6503e1.
  2. Oster AM, Brooks JT, Stryker JE, et al. Interim guidelines for prevention of sexual transmission of Zika virus-United States, 2016. MMWR Morb Mortal Wkly Rep. 2016;65(Early Release):1-2. DOI: http://dx.doi.org/10.15585/mmwr.mm6505e1er.
This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
Document FAQS.178 Version: 0
 
Effective 02/09/2016 to 05/03/2016