zika%20virus%20infection
ZIKA VIRUS INFECTION

Zika virus is an icosahedral, enveloped, single-stranded RNA virus that come from the Flaviviridae family & genus Flavivirus.

It is transmitted in humans through a bite of Aedes aegypti & Aedes albopictus mosquito.

In February 2016, the Zika virus infection was declared by the World Health Organization (WHO) as an international health emergency.

Pregnant women infected by Zika virus may pass their infection to the developing fetus & may cause birth defects such as microcephaly, ventriculomegaly, intracranial calcifications, extra-axial fluid, polymicrogyria, decreased brain parenchymal volume, hypoplasia of the cerebellum, brainstem or dermis, delayed myelination, thinning or hypoplasia of the corpus callosum & cortical atrophy & malformation.

 

 

Diagnosis

  • The preliminary diagnosis of a patient suspected with Zika virus infection should be based on clinical features, date and place of travel as well as the patient's activities

History

Important points in the clinical history of patients with suspected Zika virus infection:

  • History of recent travel to places with active Zika virus transmission
  • Unprotected sexual contact with a person who has recent exposure to Zika virus (may be vaginal, anal, oral and/or sharing of sex toys)

Laboratory Tests

RNA (Nucleic Acid Test) NAT for Non-Pregnant Women

  • The RNA in Zika virus may be detected earlier in patients who are symptomatic
  • RNA NAT should be performed 2 weeks from the onset of symptoms
    • Should be conducted on urine samples collected <14 days after the onset of symptoms
  • If there is positive result in any of the samples that has been collected, no additional tests are needed and are indicative of current infection
  • If the result is negative, then the serum collected should be further analyzed using the immunoglobulin M (IgM) antibody testing

RNA (Nucleic Acid Test) NAT for Pregnant Women

  • For symptomatic pregnant women who have exposure to Zika virus, RNA NAT testing of the serum and urine is recommended for up to 2 weeks after the onset of symptoms
  • RNA NAT of serum and urine is recommended for those asymptomatic pregnant women with <2 weeks of exposure who live in areas without active Zika transmission and were evaluated 2-12 weeks after exposure who turned out to be IgM-positive
    • Whole blood may also be tested
  • For asymptomatic pregnant patients who traveled in high-risk areas, RNA NAT testing is recommended on both serum and urine samples within 2-12 weeks from the date of last possible exposure
    • Recommended for those who present for care ≥2 weeks from being exposed and are IgM positive
  • As part of the obstetric care, asymptomatic pregnant patients are advised to have IgM testing on the 1st and 2nd trimester of pregnancy especially in areas with active virus transmission
  • For those who are IgM positive, a subsequent test known as reflex RNA NAT should be included

Trioplex Real-Time RT-Polymerase Chain Reaction (PCR) Assay

  • Used for the qualitative detection and differentiation of RNA from Zika, dengue and chikungunya virus found in human sera, whole blood (EDTA) or cerebrospinal fluid (CSF)
  • Also used for the qualitative detection of Zika virus RNA in urine and amniotic fluid
  • Negative results does not rule out Zika virus infection thus, it should not to be used as sole basis for making management decisions

Serologic Tests

  • Zika virus-specific IgM and neutralizing antibodies
    • Develop towards the end of the 1st week of illness
    • The IgM antibodies are positive on the 4th day up to 12 weeks after the onset of symptoms
    • For serum samples that has been collected ≥14 days from the onset of symptoms, it is recommended that these samples be tested for anti-Zika virus IgM antibodies
  • Zika IgM Antibody Capture Enzyme-Linked Immunosorbent Assay (Zika MAC-ELISA)
    • Detects IgM antibodies in serum or cerebrospinal fluid (CSF)
    • If the test is presumed to be positive, equivocal or inconclusive, it should be confirmed by plaque-reduction neutralization testing (PRNT)

Complications

  • Pregnant women infected by Zika virus may pass their infection to the developing fetus and may cause birth defects such as:
    • Stillbirth 
    • Microcephaly
    • Ventriculomegaly
    • Intracranial calcifications
    • Extra-axial fluid
    • Polymicrogyria
    • Decreased brain parenchymal volume
    • Hypoplasia of the cerebellum, brainstem or dermis
    • Delayed myelination
    • Thinning or hypoplasia of the corpus callosum and cortical atrophy and malformation
    • Visual defects
    • Hearing loss
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