Zika Virus

Genus: Flavivirus
1. Single-stranded RNA virus
2. Similar to Dengue, Yellow Fever, West Nile
Regions involved (CDC)
1. https://wwwnc.cdc.gov/travel/page/world-map-areas-with-zika
Transmission
1. Mosquito Bite by infected Aedes albopictus Mosquito (breeds in water containers)
  1. Primates are natural virus reservoir
  2. During epidemics, human to Mosquito to human transmission
2. Other transmission
  1. In-utero and perinatal transmission
  2. Transfusion (blood, Platelets)
  3. Sexually transmitted
    1. Zika Virus may be transmitted in semen for up to 2-6 months
    2. Peterson (2016) MMWR Morb Mortal Wkly Rep 65(39):1077-81 [PubMed]

Asymptomatic in >80% of cases
Median Incubation Period: 6 days
Duration: Typically mild symptoms for up to 1 week
Common symptomatic presentation (similar in adults and children)
1. Maculopapular rash (most common)
2. Fever
3. Nonpurulent Conjunctivitis
4. Arthralgia
Associated symptoms
1. Headache (esp. Retroorbital pain)
2. Voming
3. Myalgias
4. Edema

Preferred testing protocols for pregnant women are evolving and dependent on multiple factors
1. Timing from symptoms or exposure less than 2 weeks?
2. Symptomatic?
3. Endemic region for Zika Virus infection?
CDC Zika Diagnostics
1. http://www.cdc.gov/zika/hc-providers/diagnostic.html
Primary tests
1. Real-time reverse transcriptase PCR (RNA NAT serum and urine)
  1. Preferred test in first 2 weeks
  2. Sources
    1. Zika RNA is expected in serum from before symptoms to 1 week after (up to 10 weeks rarely)
    2. Zika RNA may be present in urine for up to 2 weeks after symptom onset
    3. Samples may also be obtained from cerebrospinal fluid and amniotic fluid
  3. Positive RNA test confirms Zika, but negative test does not exclude Zika
    1. If negative RNA, obtain Zika Virus IgM and Dengue Virus IgM
2. Serum Zika IgM
  1. Preferred test at 2-12 weeks after symptom onset
  2. False Negatives in first 2 weeks
  3. False Positives with other Flavivirus Infection (esp. previously exposed or vaccinated)
Other testing in unclear cases when primary tests are non-diagnostic
1. Dengue Virus IgM
2. Serum Plaque Reduction Neutralization Testing (serum PRNT)
  1. Indicated in positive or equivocal Zika Virus IgM
  2. False Positives due to cross reactivity with Dengue Virus (avoid in Puerto Rico)

Exclude serious causes in differential (e.g. Dengue Fever)
Supportive Care
Hydration
Analgesics (e.g. NSAIDs, Acetaminophen)
1. Avoid NSAIDs until Dengue Fever is excluded
2. Avoid Aspirin (due to Thrombocytopenia risk in Zika, Hemorrhage risk in Dengue Fever)
Reduce transmission to others
1. Prevent further Mosquito Bites during acute Zika Virus infection
2. Prevent sexual transmission

Congenital Zika Syndrome (with severe Microcephaly and associated neurologic complications)
Guillain-Barre Syndrome (also occurs with West Nile Virus)
1. Risk following Zika Infection: 0.24 per 1000
2. Median onset of neurologic findings after Zika Infection: 5-6 days
Thrombocytopenia
1. May be severe, life threatening (rare)
Zika Virus Encephalitis

See Prevention of Vector-borne Infection
Pregnant women in Zika active regions
1. Pregnant women in Zika active regions should use Condoms or abstinence throughout pregnancy
2. Guidance for pregnant women with Zika Exposure (CDC)
  1. https://www.cdc.gov/mmwr/volumes/65/wr/mm6539e1.htm?s_cid=mm6539e1_w
Nonpregnant women in Zika active regions
1. Strongly consider effective Contraception if not desiring pregnancy
Sexual transmission prevention
1. Women should use Condoms or abstinence for at least 2 months after infection or exposure
2. Men should use Condoms to prevent transmission
  1. Use Condoms for 6 months after Zika infection (or when attempting conception after exposure) AND
  2. Use Condoms for 8 weeks after traveling to Zika endemic region