Zika Virus

Essentials of Diagnosis

• Most infected persons asymptomatically seroconvert

• Clinical symptoms are akin to those of chikungunya virus infection but with less arthritis

• Complications include microcephalic infants and ocular abnormalities born to mothers infected during pregnancy as well as Guillain-Barré

• There is no effective antiviral or vaccine

General Considerations

• Zika virus is a flavivirus, akin to the viruses that cause dengue fever, Japanese encephalitis, and West Nile infection

• Aedes species mosquitoes, particularly Aedes aegypti, are responsible for transmission of Zika virus

• The biodistribution of the species largely determines the area of prevalence for Zika virus

• Aedes species mosquitoes are found primarily in the southeastern United States, but one species Aedes albopictus (the Asian tiger mosquito known to sequester in tires) may be seen as far north as Pennsylvania

• Modes of transmission

  • Sexual: reported from males and females to partners via vaginal, anal, or oral sex

  • Vertical: from pregnant woman to fetus is prominent

  • Via platelet transfusion has also been reported

Demographics

• The virus was noted in Africa and Asia during the 1950s–1980s

• A large outbreak occurred in French Polynesia in 2013

• A smaller outbreak occurred on Easter Island during 2014

• Noted in Brazil in 2015; 239,742 cases were subsequently reported between 2015 and 2018

• As of November 7, 2019, there have been 15 cases (14 in travelers and 1 laboratory-acquired case) in the United States and 51 (49 locally-acquired cases and 2 travel-associated cases) in the US territories

Symptoms and Signs

• Incubation period is about 3–14 days

• Most infections (50–80%) are asymptomatic

• Acute onset fever

• Maculopapular rash that is often pruritic

• Nonpurulent conjunctivitis

• Arthralgias

• Rash may outlast the fever but is not always present

• Symptoms last up to 7 days

Differential Diagnosis

• Dengue

• Chikungunya virus infection

• The CDC recommends that everyone with symptoms of Zika infection be tested if they have traveled to an endemic area with active transmission

• Diagnosis is made by detecting viral RNA (nucleic acid testing, NAT) in patients presenting with onset of symptoms less than 7 days

  • NAT can be performed within 14 days of illness onset

  • Persons being tested 14 days or more after symptom onset should be tested using IgM serology

• The Trioplex real-time PCR assay, which detects Zika virus, chikungunya virus, and dengue virus RNA, and the Zika MAC-ELISA, which detects Zika virus IgM antibodies (usually present up to 12 weeks after illness onset), are available

• Matched serum and urine specimens should be tested simultaneously

• There are no effective antivirals against Zika virus

• Sofosbuvir

  • Shows some ability to inhibit Zika replication and infection in vitro

  • Appears to be synergistic with interferon-alpha and with interferon-beta

• Aspirin does not appear to be associated with major hemorrhagic complications as seen in dengue

Complications

• Congenital microcephaly

• Ocular findings, including ocular lesions of chorioretinal atrophy and focal pigmented mottling of the retina

• Guillain-Barré syndrome

• Can persist in semen for months

Prevention

• Environmental control of mosquitoes