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For informational purposes only — not medical advice
How serious?
Risk of death
No
Vaccine available?
Time to symptoms
Countries affected
Active outbreaks
Low risk for most travelers. Pregnant women or those planning pregnancy should consult their doctor before traveling to Zika-endemic areas. Use mosquito repellent consistently. Sexual transmission is possible — use protection for 3 months after travel to endemic areas.
Mosquito-borne viral disease usually causing mild illness in adults but associated with severe birth defects (microcephaly) when contracted during pregnancy. No vaccine available.
Symptoms | Frequency | Severity | Onset |
|---|---|---|---|
| Arthralgia | 65% | Mild | Early |
| Conjunctivitis | 55% | Mild | Early |
| Fever | 65% | Mild | Early |
| Maculopapular rash | 90% | Mild | Early |
| Fatigue | 60% | Mild | Early |
| Headache | 45% | Mild | Early |
| Itching | 40% | Mild | Early |
| Malaise | 50% | Mild | Early |
| Myalgia | 48% | Mild | Early |
| Retro-orbital pain | 35% | Mild | Early |
| Nausea | 20% | Mild | Early |
| Swollen lymph nodes | 15% | Mild | Early |
| Abdominal pain | 7% | Mild | Early |
| Diarrhea | 8% | Mild | Early |
| Dizziness | 10% | Mild | Early |
| Loss of appetite | 15% | Mild | Early |
| Vomiting | 10% | Mild | Early |
| Edema | 5% | Mild | Peak |
Zika virus disease is caused by the Zika virus (ZIKV), a mosquito-borne flavivirus of the family Flaviviridae, closely related to dengue, yellow fever, and Japanese encephalitis viruses. The primary vector is the Aedes aegypti mosquito, with Aedes albopictus serving as a secondary vector. Uniquely among arboviruses, Zika is also transmitted through sexual contact, perinatal (mother-to-child) transmission, blood transfusion, and possibly breast milk.
First identified in 1947 from a sentinel rhesus monkey in the Zika Forest of Uganda, the virus caused only sporadic human cases for decades. The first major outbreak occurred in Yap State, Federated States of Micronesia, in 2007, followed by a large epidemic in French Polynesia in 2013–2014. The 2015–2016 epidemic in the Americas, centered in Brazil, revealed the devastating neurotropic potential of ZIKV, with confirmed causal links to congenital Zika syndrome (CZS) — characterized by microcephaly and severe brain abnormalities in fetuses and neonates — and Guillain-Barré syndrome (GBS) in adults.
The WHO declared the Zika epidemic a Public Health Emergency of International Concern (PHEIC) in February 2016, which was lifted in November 2016. While the epidemic wave subsided due to population immunity, ZIKV continues to circulate at low levels in tropical regions of the Americas, Africa, Southeast Asia, and the Pacific Islands, with the potential for future outbreaks in areas with naive populations and competent Aedes mosquito vectors.
Causative agent: Zika virus (ZIKV), an enveloped, single-stranded positive-sense RNA virus of the genus Flavivirus. Two lineages: African and Asian (the Asian lineage caused the Americas epidemic).
Transmission routes:
Mosquito-borne (primary): Aedes aegypti (tropical/subtropical) and Ae. albopictus (temperate, expanding range). Day-biting mosquitoes that breed in small water containers near human habitation.
Sexual transmission: Documented male-to-female, male-to-male, and female-to-male. Virus persists in semen for up to 6 months (longest of any arbovirus), in vaginal secretions for up to 2 weeks.
Perinatal (vertical): Mother-to-child transmission occurs during pregnancy (transplacental) and possibly during delivery. Risk of fetal damage is highest in the first trimester but exists throughout pregnancy.
Blood transfusion: Documented during the 2015–2016 epidemic. Screening of blood donations implemented in endemic areas.
Incubation period: 3–14 days (most commonly 3–7 days).
Epidemiological status (2024): Low-level endemic circulation in 89+ countries across the Americas, Africa, Southeast Asia, and the Pacific. Risk of large-scale outbreaks persists where susceptible populations and Aedes vectors coexist. No vaccine currently available.
Seek immediate medical attention if any of the following develop during or after Zika virus infection:
Signs of Guillain-Barré syndrome (GBS):
Progressive weakness starting in the legs and ascending upward (ascending paralysis)
Tingling, numbness, or "pins and needles" sensation in the feet and hands
Difficulty walking, climbing stairs, or rising from a chair
Facial weakness (difficulty smiling, closing eyes, or drinking through a straw)
Difficulty swallowing or speaking
Difficulty breathing or shortness of breath — this is a medical emergency as respiratory failure can develop rapidly and may require mechanical ventilation
GBS typically develops 1–4 weeks after acute Zika infection; estimated incidence is 2–3 per 10,000 Zika infections
Pregnancy-related concerns:
Any pregnant woman with symptoms compatible with Zika (rash, fever, conjunctivitis) or who has traveled to a Zika-endemic area should seek immediate obstetric and infectious disease consultation, regardless of symptom severity
Ultrasound findings of microcephaly, intracranial calcifications, or other brain abnormalities in the fetus of a woman with possible Zika exposure require urgent specialist referral
Diagnostic confusion with dengue:
In areas where both dengue and Zika co-circulate, warning signs of severe dengue (abdominal pain, persistent vomiting, mucosal bleeding, lethargy, hepatomegaly, rapid platelet decline) should be treated as dengue warning signs until proven otherwise, as severe dengue can be life-threatening
Do not use NSAIDs or aspirin until dengue has been excluded (risk of hemorrhagic complications)
Most common signs and symptoms
Asymptomatic infection (80%): The majority of Zika virus infections cause no symptoms. These individuals still develop viremia, can transmit the virus to mosquitoes and sexual partners, and — critically — can transmit the virus transplacentally to a developing fetus.
Symptomatic disease (20%) — typically mild and self-limiting:
Maculopapular rash: Often the first and most prominent symptom. Pruritic (itchy), beginning on the face and trunk, spreading to the extremities. Present in ~90% of symptomatic cases. Distinctive feature that helps differentiate from dengue.
Low-grade fever: 37.5–38.5°C, rarely exceeding 39°C. Lower than typical dengue fever.
Non-purulent conjunctivitis: Bilateral conjunctival hyperemia without discharge, present in 55–65% of symptomatic cases. Relatively specific to Zika among arboviruses.
Arthralgia: Bilateral, symmetric, involving small joints of hands and feet, wrists, ankles, and knees. Less severe than chikungunya but may persist for weeks.
Headache, myalgia, retro-orbital pain: Common but usually mild.
Other: Peripheral edema of hands and feet, abdominal pain, diarrhea, aphthous ulcers.
Duration of illness: Symptoms typically resolve within 2–7 days. Arthralgia may persist for 2–4 weeks. Fatigue may linger for several weeks.
Important clinical note: The mildness of acute Zika infection belies its potential for devastating consequences — congenital Zika syndrome in pregnancies and Guillain-Barré syndrome. A mild or even asymptomatic maternal infection during pregnancy can cause severe, permanent damage to the developing fetal brain.
Knowing the symptoms is the first step to a quick response.
Typical disease course:
Key differences from dengue: Zika has milder fever, more prominent rash and conjunctivitis, and rarely causes severe thrombocytopenia or hemorrhage. The major threat is congenital Zika syndrome, not acute disease severity.
Sexual transmission window: Males should use condoms or abstain for 3 months after Zika infection/travel to endemic areas. Females: 2 months.
How this disease is identified
Molecular diagnosis (preferred in the acute phase):
RT-PCR: Detection of ZIKV RNA in serum and urine. Sensitivity is highest within the first 7 days of symptom onset (viremic period). Urine RT-PCR may remain positive for 2–3 weeks, extending the diagnostic window.
Serum: ZIKV RNA detectable from 1–2 days before symptom onset through 5–7 days after.
Urine: Higher viral loads and longer detection period than serum. Preferred specimen when RT-PCR is the primary diagnostic method.
Whole blood: May extend detection window further (up to 60+ days in some studies), but not yet widely standardized.
Serological diagnosis:
IgM ELISA: ZIKV-specific IgM appears 4–7 days after symptom onset and may persist for 2–12 weeks (sometimes months). However, extensive cross-reactivity with other flaviviruses (especially dengue) limits specificity.
IgG ELISA: Even more cross-reactive than IgM. Difficult to interpret in individuals with prior dengue or yellow fever vaccination.
Plaque reduction neutralization test (PRNT): The most specific serological test. A ≥4-fold rise in ZIKV-specific neutralizing antibody titer, with titers ≥4-fold higher than for other flaviviruses, confirms Zika infection. Resource-intensive and available only at reference laboratories.
Diagnosis in pregnancy:
RT-PCR of serum and urine at first prenatal visit and after possible exposure
If RT-PCR negative but clinical/epidemiological suspicion exists, IgM ELISA followed by PRNT
Amniocentesis: ZIKV RT-PCR on amniotic fluid may be considered after 15 weeks gestation in confirmed or probable maternal infection
Serial fetal ultrasounds to detect microcephaly and other CNS abnormalities
Differential diagnosis: Dengue, chikungunya, rubella, parvovirus B19, measles, rickettsial diseases, leptospirosis, HIV seroconversion. Co-infection with dengue and/or chikungunya is common in endemic areas.
Available treatment methods
There is no specific antiviral treatment for Zika virus infection. Management is supportive and focuses on symptom relief and monitoring for complications.
Symptomatic treatment of acute Zika:
Rest and adequate fluid intake
Paracetamol (acetaminophen) for fever and pain
Avoid NSAIDs and aspirin until dengue has been excluded, as these can worsen bleeding in dengue hemorrhagic fever. In areas where dengue co-circulates, dengue should be ruled out before using ibuprofen or aspirin. Once dengue is excluded, NSAIDs may be used for arthralgia.
Antihistamines (oral cetirizine, loratadine) for pruritic rash
No need for hospitalization in uncomplicated cases
Management of Guillain-Barré syndrome (GBS):
Hospitalization in a facility with intensive care capability
Intravenous immunoglobulin (IVIG) or plasmapheresis — both are equally effective first-line treatments
Monitoring of respiratory function (forced vital capacity every 4–6 hours) as respiratory failure may develop rapidly
Mechanical ventilation if vital capacity falls below 20 mL/kg or 1 liter
DVT prophylaxis, pain management, and early rehabilitation
Recovery from Zika-associated GBS is generally favorable, with 60–80% achieving full functional recovery within 12 months
Management during pregnancy:
Serial ultrasound surveillance for fetal abnormalities (every 3–4 weeks)
Amniocentesis with Zika RT-PCR may be considered after 15 weeks gestation
Multidisciplinary care involving maternal-fetal medicine, pediatric neurology, and infectious disease
No treatment can reverse or prevent congenital Zika syndrome once infection has occurred
Genetic counseling and psychological support for affected families
Most cases are effectively treated with early diagnosis.
How to protect yourself
No vaccine is currently available for Zika virus. Several candidates are in clinical trials (DNA vaccines, mRNA vaccines, purified inactivated, live-attenuated), but none has yet been licensed. Prevention relies entirely on vector control, personal protective measures, and behavioral modifications.
Mosquito bite prevention:
Use EPA-registered insect repellents containing DEET (20–50%), picaridin (20%), IR3535, or oil of lemon eucalyptus on exposed skin. Reapply as directed.
Wear long-sleeved shirts and long trousers, preferably light-colored and permethrin-treated.
Sleep under insecticide-treated mosquito nets (ITNs), especially if accommodations are not screened or air-conditioned.
Aedes mosquitoes bite primarily during daytime hours (peak: early morning and late afternoon), unlike Anopheles (malaria) which bites at night. Daytime protection is essential.
Eliminate standing water around living areas: flower pots, tires, buckets, water storage containers are prime breeding sites for Aedes mosquitoes.
Prevention of sexual transmission:
CDC recommends that men with confirmed or suspected Zika infection use condoms or abstain from sex for at least 3 months after symptom onset (due to prolonged viral shedding in semen).
Women with confirmed or suspected Zika should use condoms or abstain for at least 2 months after symptom onset.
Couples in which either partner has traveled to a Zika-endemic area should use barrier contraception for the recommended period, even if asymptomatic, as 80% of infections are asymptomatic.
Prevention of congenital Zika syndrome:
Pregnant women should avoid travel to areas with active Zika transmission — the single most important recommendation.
Women planning pregnancy should wait at least 2 months after return from an endemic area (or 3 months if their male partner was also exposed) before attempting conception.
In endemic areas, women of reproductive age should have access to contraception and comprehensive counseling about Zika risks.
Preparation is the best protection.
Pre-travel risk assessment:
Check the CDC and WHO websites for current Zika transmission status in your destination. Risk areas include tropical and subtropical regions of the Americas, the Caribbean, Africa, Southeast Asia, and the Pacific Islands.
Assess personal risk factors: pregnancy status, plans for pregnancy, immunocompromised status.
Critical advice for pregnant women and couples planning pregnancy:
Pregnant women should not travel to areas with active Zika virus transmission. This recommendation applies to all trimesters, as fetal damage can occur at any stage of pregnancy. The risk is highest in the first trimester, with congenital Zika syndrome affecting 5–15% of fetuses exposed during this period.
Women planning pregnancy should wait at least 2 months after returning from a Zika area before attempting conception.
If the male partner traveled to a Zika area, the couple should wait at least 3 months before attempting conception (due to prolonged viral persistence in semen).
Use condoms consistently during pregnancy if the partner has traveled to an endemic area.
During travel:
Apply strict mosquito bite prevention measures at all times of day, especially during morning and afternoon hours when Aedes mosquitoes are most active.
Stay in screened or air-conditioned accommodations.
Use condoms for all sexual encounters during travel and for the recommended period after return.
Post-travel:
If you develop a rash, fever, joint pain, or red eyes within 2 weeks of returning from a Zika-endemic area, seek medical attention and inform your clinician of your travel history.
If you are pregnant and have traveled to a Zika-endemic area (even without symptoms), consult your obstetrician for testing and surveillance.
Follow the recommended waiting periods before attempting conception after return.
Statistics and geographic data
Historical emergence:
1947: ZIKV isolated from a febrile sentinel rhesus monkey in the Zika Forest, Uganda. First human cases identified in 1952 (Uganda and Tanzania).
1947–2006: Only 14 documented human cases worldwide — the virus was considered an obscure, benign pathogen.
2007: First major outbreak on Yap Island, Federated States of Micronesia. An estimated 73% of the population infected; no hospitalizations, no neurological complications recognized.
2013–2014: Large epidemic in French Polynesia (~32,000 cases). Retrospective analysis revealed the first association with Guillain-Barré syndrome (42 cases during the outbreak).
2015–2016 Americas epidemic:
The pandemic wave began in northeast Brazil in early 2015, spreading rapidly through the Americas. By 2017, 48 countries and territories in the Americas reported autochthonous transmission.
Brazil: >200,000 suspected cases, >3,000 confirmed cases of microcephaly (a 20-fold increase over baseline).
The Americas epidemic confirmed the causal link between ZIKV and congenital Zika syndrome (WHO, April 2016) and Guillain-Barré syndrome.
Total: 89 countries and territories have reported evidence of mosquito-borne ZIKV transmission as of 2024.
Current status (2024):
Transmission has declined substantially from the 2016 peak due to high population immunity in previously affected areas. However, low-level circulation continues in tropical Americas, Southeast Asia, Africa, and the Pacific.
The risk of future outbreaks persists in areas with naive populations, competent Aedes vectors, and favorable climate conditions. Climate change is expanding the geographic range of Aedes mosquitoes into previously temperate regions (southern Europe, southern USA).
Surveillance gaps: ZIKV circulation in Africa and Southeast Asia is likely underestimated due to limited diagnostic capacity and the mildness of most infections.
Who is most at risk
Risk factors for Zika virus infection:
Geographic exposure: Living in or traveling to tropical and subtropical regions where Aedes aegypti and Ae. albopictus mosquitoes are present and ZIKV is circulating. The highest transmission occurred in the Americas (2015–2017), but the virus circulates in Africa, Southeast Asia, and the Pacific.
Mosquito exposure: Outdoor activities during daytime hours, lack of screened windows or air conditioning, proximity to standing water and urban breeding sites.
Sexual exposure: Unprotected sexual contact with a partner who has been infected or traveled to an endemic area. Risk persists for weeks to months after acute infection, particularly from male partners (viral shedding in semen up to 6 months).
Occupational risk: Outdoor workers in endemic areas, laboratory personnel handling ZIKV specimens, healthcare workers in endemic regions.
Risk factors for severe outcomes (congenital Zika syndrome):
Pregnancy: The single most important risk factor for devastating consequences. Infection during the first trimester carries the highest risk of congenital abnormalities (5–15%), but damage can occur at any gestational age.
First infection vs. re-infection: Primary ZIKV infection during pregnancy poses the greatest risk. Whether prior immunity (from previous infection or future vaccination) is fully protective against congenital syndrome remains under study.
Risk factors for Guillain-Barré syndrome:
The mechanism linking ZIKV to GBS is not fully understood but likely involves molecular mimicry between viral antigens and gangliosides on peripheral nerve myelin.
Incidence: approximately 2–3 GBS cases per 10,000 ZIKV infections. Male sex and age over 40 may confer slightly higher risk.
Prior dengue infection: some evidence suggests that sequential flavivirus infections may modulate immune responses, but the role of antibody-dependent enhancement (ADE) in Zika-associated GBS remains debated.
Potential complications
Congenital Zika syndrome (CZS) — the most devastating complication:
CZS results from vertical (transplacental) transmission of ZIKV to the developing fetus. Risk of CZS is highest with first-trimester infection (5–15%) but exists throughout pregnancy.
Microcephaly: Head circumference >2 standard deviations below the mean for gestational age. Severe microcephaly (>3 SD below mean) with partially collapsed skull is the hallmark feature.
Brain abnormalities: Cortical thinning, gyral abnormalities (lissencephaly, pachygyria), subcortical calcifications (especially at the cortico-subcortical junction), ventriculomegaly, cerebellar and brainstem hypoplasia.
Ocular abnormalities: Chorioretinal atrophy and focal pigmentary mottling (present in 30–40% of CZS cases), optic nerve hypoplasia, micro-ophthalmia.
Musculoskeletal: Congenital contractures (arthrogryposis), especially of lower limbs. Clubfoot.
Neurodevelopmental outcomes: Severe intellectual disability, seizures (occurs in ~50%), spasticity, feeding difficulties, vision and hearing impairment. Most children with severe CZS require lifelong care.
Subclinical congenital infection: Some infants born to infected mothers have normal head circumference at birth but develop neurodevelopmental abnormalities (cognitive, motor, visual, auditory) in the first years of life, highlighting the importance of long-term follow-up.
Guillain-Barré syndrome (GBS):
Acute inflammatory demyelinating polyneuropathy triggered by post-infectious immune response.
Incidence: 2–3 cases per 10,000 ZIKV infections (approximately 10-fold the background GBS rate).
Presents 1–4 weeks after acute Zika infection with ascending symmetric weakness, areflexia, and potential respiratory failure.
With appropriate ICU care (IVIG or plasmapheresis, respiratory support), mortality is 3–7%. Full recovery in 60–80% within 12 months, but 5–10% have persistent disability.
Other reported complications:
Acute myelitis: rare, with paraplegia or tetraplegia
Meningoencephalitis: uncommon, primarily in immunocompromised individuals
Immune thrombocytopenic purpura: case reports
Myocarditis: isolated case reports
Expected outcomes and recovery
In non-pregnant adults: Excellent prognosis. Self-limiting illness lasting 2–7 days. CFR extremely low (<0.01%).
In pregnancy: DEVASTATING fetal consequences.
Congenital Zika syndrome: microcephaly, brain calcifications, ocular abnormalities, arthrogryposis, growth restriction.
Risk of congenital abnormalities: 5–15% of first-trimester infections (some estimates higher).
First trimester infection carries the highest risk.
Guillain-Barré syndrome (GBS): 2–3 per 10,000 infections. Usually self-limiting but may require ICU care.
Long-term: No chronic infection. Post-infection immunity appears durable.
The content on this page is for informational and educational purposes only. It does not constitute medical advice, diagnosis, or treatment recommendations. If you have health concerns, consult a qualified healthcare professional. Medova is not a medical service provider.
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