Virus Zika : transmission, risques et prévention | Clinique Omicron

Transmission

• Vector (main): sting of Aedes aegypti + and Aedes albopictus (tiger mosquito) → active during the day + mainly in the morning and late afternoon + in tropical and subtropical areas
• Sexual (unique feature among arboviruses): sexual transmission documented → virus detectable in semen up to 6 months after symptomatic infection + and 3 months after asymptomatic infection → particularly important transmission route for prevention in case of pregnant partner
• Maternal-fetal (transplacental): transmission to the fetus at any stage of pregnancy → maximum risk in the 1st trimester (cerebral organogenesis) + but complications possible throughout the pregnancy
• Blood transfusion + transplant: documented cases + systematic screening of blood donations in endemic areas
• Breastfeeding ZIKV detected in breast milk + but transmission to the breastfed infant not documented + breastfeeding is not contraindicated

Clinical Presentations

• Asymptomatic infection (80 % of cases): The vast majority of Zika infections are silent and asymptomatic, with seroconversion possible and discovered retrospectively.
• Zika Fever (% of cases): Mild to moderate febrile syndrome + incubation period of 3–14 days + moderate fever (often absent or mild) + pruritic maculopapular exanthem (generalized pink rash — most suggestive symptom) + bilateral non-purulent conjunctivitis (characteristic — distinguishes from chikungunya) + arthralgia + myalgia + headache + duration of 2–7 days + spontaneous resolution + no documented deaths in immunocompetent adults
• Guillain-Barré Syndrome (neurological complication - 1 in 4,000 infections): acute inflammatory demyelinating polyradiculoneuropathy → progressive muscle weakness + areflexia + risk of respiratory failure + 20-fold increased incidence in affected countries during outbreaks → hospitalization + IV immunoglobulins + or plasma exchange
• Congenital Zika Syndrome microcephaly (head circumference <-2 DS) + periventricular intracranial calcifications + cortical malformations (lissencephaly + polymicrogyria) + ventriculomegaly + cerebral atrophy + hearing impairment + ophthalmological disorders + arthrogryposis + risk of microcephaly estimated at 1-13 % of maternal-fetal infections in the 1st trimester

Diagnosis

• RT-PCR Zika (blood + urine + sperm): Direct detection of viral RNA → blood: positive up to D7 after symptom onset + urine: positive longer (up to D20) → simultaneously test blood AND urine to maximize sensitivity + sperm: positive up to 6 months
• Zika IgM + IgG Serology: Detectable IgM from D4–D5 + IgG from D7 → significant cross-reactions with dengue and other flaviviruses → plaque reduction neutralization tests (PRNT) needed for specific confirmation + available at reference laboratories (LNSP + Health Canada)
• In pregnant women returning from an endemic area: RT-PCR positive, urine within 2 weeks post-exposure, serology if RT-PCR negative, serial obstetric ultrasound (microcephaly + calcifications), and specialized maternal-fetal medicine evaluation.
• Dengue/Zika cross-reactions: Zika IgM serologies can be falsely positive in cases of recent or past dengue infection → always interpret with clinical and epidemiological data + confirmatory tests (PRNT)

Prevention — particularly for pregnant travelers

• Advice for pregnant women: Avoid all travel to areas with active ZIKV transmission during pregnancy → if travel is unavoidable → maximum mosquito protection (DEET 20–30 % + covering clothing + mosquito nets) + protected sex (condom) throughout pregnancy if partner exposed
• Time before conception after returning from an endemic area (Health Canada 2023): Woman who traveled with Zika symptoms → wait 2 months before pregnancy + woman who traveled without symptoms → wait 2 months + man who traveled with symptoms → wait 6 months (presence of the virus in sperm up to 6 months) + man who traveled without symptoms → wait 3 months
• Mosquito repellent: DEET 20–30 % (safe en grossesse après le 1er trimestre) + icaridine 20 % + vêtements manches longues + moustiquaires imprégnées + climatisation + Aedes pique le jour → protection constante jour et nuit
• Prevention of sexual transmission: male or female condom + or abstinence → throughout pregnancy if partner has stayed in an endemic area → even if asymptomatic (80 % of infections are asymptomatic)
• Vaccine No Zika vaccine approved to date + several candidates in Phase II-III clinical trials

Consult at Clinique Omicron

Clinique Omicron's Nurse Practitioners and Physicians (NPPs) provide pre-travel consultations for Zika-affected areas (DEET advice + clothing + condoms + conception delays), prescribe post-exposure Zika RT-PCR blood and urine tests + serology, refer exposed pregnant women to maternal-fetal medicine for ultrasound monitoring, evaluate post-travel neurological symptoms compatible with GBS, and follow up with symptomatic travelers returning from endemic areas. Consultations are available at several service points in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.

The content of this page is provided for informational purposes only and does not replace the advice of a doctor or a travel medicine specialist. Recommendations on timing before conception and preventive measures evolve according to epidemiological alerts—always consult the latest travel advisories from the Public Health Agency of Canada (PHAC) before any departure to an endemic area. There is currently no vaccine against the Zika virus.