Zika Virus Infection

Summary

Zika virus, spread mainly by Aedes mosquitoes, usually causes mild or no symptoms but can lead to Guillain–Barré syndrome in adults and severe congenital defects in infants. Diagnosis is by RT-PCR, treatment is supportive, and prevention depends on mosquito control, safe sex, and avoiding exposure in pregnancy.

Epidemiology

• Worldwide distribution, mainly in tropical and subtropical regions.

• Before 2015: sporadic cases in Africa, Southeast Asia, Pacific Islands.

• Since 2015: major outbreaks in South America (esp. Brazil).

• United States:

• Most cases are travel-related.

• 2016 outbreak: ~4000 locally acquired cases, mainly in Puerto Rico.

Etiology

• Pathogen: Zika virus (Flavivirus, arbovirus).

• Genome: Positive-sense, single-stranded, enveloped RNA virus.

Transmission

• Mosquito-borne: Aedes aegypti (most common; daytime biting).

• Other routes:

  • Transplacental (mother → fetus).

  • Sexual transmission.

  • Rare: blood transfusion.

Clinical Features

• Incubation period: 2–14 days.

• ~80% asymptomatic.

• Symptomatic disease: mild, lasts 2–7 days.

• Manifestations:

• Low-grade fever.

• Headache, arthralgia, myalgia, malaise.

• Non-purulent conjunctivitis.

• Pruritic maculopapular rash (~20%).

Diagnosis

• Clinical suspicion: Compatible symptoms + travel/sexual exposure history.

• Laboratory findings (nonspecific): leukopenia, thrombocytopenia.

• Confirmatory tests:

• NAAT (e.g., RT-PCR) → detects viral RNA, preferred early test.

• Serology (IgM) → supportive but cross-reactive.

• Pregnancy: may test placenta, amniotic fluid, or fetal tissues.

Management

• No curative therapy (supportive care only):

• Rest, hydration, acetaminophen.

• Avoid NSAIDs/aspirin until dengue is excluded.

• Public health: Zika infection is a nationally notifiable disease.

Complications

• Neurological: Guillain–Barré syndrome.

• Congenital Zika syndrome (CZS):

• Microcephaly, craniofacial disproportion.

• Ventriculomegaly, intracranial calcifications.

• Spasticity, contractures, seizures, hyperreflexia.

• Ocular abnormalities (e.g., retinal mottling).

• Sensorineural hearing loss.

• Miscarriage.

Prevention

• No vaccine available.

• Vector control: insect repellents, nets, long sleeves.

• Sexual precautions:

• Women: wait ≥2 months after exposure before conception.

• Men: wait ≥3 months.

• During pregnancy:

• Avoid endemic regions.

• Abstain from unprotected sex if partner exposed.