1. Executive Summary: Key Findings

• As of December 2023, 92 countries and territories have documented autochthonous (locally acquired) mosquito-borne Zika virus (ZIKV) transmission. [1, 2]
• Global case counts peaked in 2016, driven by a large-scale epidemic originating in Brazil. An estimated 500,000+ cases were reported in the Americas during 2015–2016. [3]
• The WHO declared a Public Health Emergency of International Concern (PHEIC) from February to November 2016. [4]
• Post-2017, reported global cases declined substantially; however, low-level transmission continues in the Americas, Southeast Asia, the Western Pacific, and Africa. [1, 5]
• PAHO reported 42,127 suspected cases (including 1,998 laboratory-confirmed) across the Americas in 2024, led by Brazil (>40,000 suspected cases). [6]
• Brazil reported 22,831 cases by November 1, 2025, continuing as the highest-burden country globally. [7]
• India reported 151 confirmed cases in 2024 across three states (Maharashtra, Karnataka, Gujarat) — its highest count since Maharashtra first reported cases in 2021. [8]
• No currently approved vaccine exists for ZIKV. The most advanced candidate (Valneva VLA1601) entered Phase 1 clinical trials in 2025. [9]
• True case burden globally is substantially higher than reported due to approximately 80% of infections being asymptomatic and widespread surveillance gaps. [10]

2. Global Zika Virus Overview

3. Zika Virus: Historical Global Trends (2010–2025)

The table below presents confirmed and estimated global case counts by year. Data for the Americas are drawn from PAHO surveillance records; global totals prior to 2015 reflect limited case detection in Pacific Island outbreaks and sporadic reporting.

4. Zika Cases by Country — Master Data Table

Note on data comparability: PAHO country totals include both suspected and laboratory-confirmed cases. Some countries report confirmed cases only. Country figures are therefore not directly comparable. [17]

5. Zika Virus Regional Distribution Analysis

6. Active vs. Past Zika Virus Transmission Countries

7. Country Wise Zika Virus Cases

7.1 Brazil — Epicenter of Global Outbreak

Brazil reported its first Zika cases in May 2015 and subsequently became the epicenter of the largest ZIKV outbreak in recorded history. An estimated 500,000+ cases were reported in the Americas during 2015–2016, with Brazil accounting for the vast majority. [3] In October 2015, Brazilian clinicians detected a marked increase in neonatal microcephaly cases in the northeast, which was later causally linked to ZIKV infection. [4]

Post-epidemic surveillance data: Brazil’s Ministry of Health reported approximately 274,000 suspected cases in 2016. [33] This figure declined substantially after 2017, reaching approximately 35,962 suspected cases in 2023. In 2024, PAHO documented 40,891 suspected cases (of which 1,998 were laboratory-confirmed) as of December 7, 2024. [6] By November 1, 2025, Brazil had already recorded 22,831 cases for the year, with the majority concentrated in Sao Paulo state. [7]

7.2 India — Emerging Localized Clusters

India reported its first ZIKV case in Gujarat State in 2016. [21] Subsequent outbreaks occurred in Tamil Nadu (2017), Rajasthan (2018, 159 cases including 64 pregnant women), Madhya Pradesh (2018, 130 cases — at the time the largest documented cluster in Southeast Asia), Kerala (2020, ~70 cases; 2021, 1 case), Uttar Pradesh (2021), and Karnataka (2022–2023). [21, 22]

In 2024, a localized outbreak occurred in Maharashtra state, originating in Pune. The index case was identified on June 20, 2024, in a 46-year-old male presenting with fever, rash, arthralgia, myalgia, and thrombocytopenia. WHO’s Disease Outbreak Notice (DON 549, January 29, 2025) confirmed 151 total cases in 2024 across three states: Maharashtra (140 cases, of which 125 were from Pune district), Karnataka (10 cases), and Gujarat (1 case). No cases of microcephaly or Guillain-Barré syndrome were reported in association with this outbreak as of December 31, 2024. [8]

7.3 United States — Travel-Associated Only

The continental United States has not reported locally acquired ZIKV transmission since 2019. In 2024, CDC recorded 19 non-congenital Zika cases among U.S. residents, of which the predominant route was travel-associated. One locally acquired case was reported in Texas. Puerto Rico, classified as a risk territory due to established Aedes aegypti populations, reported 16 cases in 2024. [14]

In 2025, six travel-associated cases were documented in the continental U.S., with one locally acquired case. The Hawaii Department of Health announced two travel-related cases in May 2025. [19] Since 2019, no confirmed Zika cases have been reported from U.S. territories including Puerto Rico, as antibody-based testing cannot distinguish recent from prior infection. [14]

7.4 Southeast Asia — Endemic Background Transmission

Southeast Asia has a long history of ZIKV circulation predating the Americas epidemic. Following the 2015–2016 epidemic, clusters were documented in multiple countries. Specifically: Singapore reported a cluster in 2023; Thailand reported cases in 2023–2024; Bangladesh documented a cluster of 10 locally acquired cases near Dhaka between September and December 2024; Sri Lanka was retrospectively added to the WHO country list based on specimen testing from 2022–2023. [1, 2, 19]

Exact case counts for Thailand, Vietnam, Indonesia, and the Philippines are not publicly available at the national level from WHO or Ministry of Health bulletins reviewed for this report. Data should be treated as confirmed presence of transmission but not as precise burden estimates.

7.5 Americas Regional Highlights (Beyond Brazil)

As of February 18, 2025, PAHO confirmed ZIKV activity in eight countries in the Americas: Brazil, Bolivia, Colombia, Costa Rica, El Salvador, Guatemala, Mexico, and Peru. [18] Bolivia (1,024 cases) and Argentina (892 confirmed) emerged as the second and third highest-reporting countries in 2025 as of November. [16] Mexico reported 30 cases in 2024 and 3 cases by February 2025. [6, 18] Since 2015, PAHO has documented ZIKV transmission across 52 countries and territories in the Americas. [17]

8. Zika Virus: Transmission & Vector Distribution

8.1 Primary Vectors

Zika virus is primarily transmitted by Aedes aegypti mosquitoes in tropical and subtropical regions. Aedes albopictus (the Asian tiger mosquito) is a secondary vector with a broader geographic range, extending into temperate climates including parts of Europe and North America. ZIKV transmission by Ae. albopictus has been documented experimentally and in field conditions. [5, 7]

Additional documented transmission routes include: mother-to-fetus (vertical transmission during pregnancy), sexual contact, blood transfusion, and potential organ transplantation. [5] Breast milk transmission has been detected by PCR but has not been confirmed as a practical transmission route. [35]

8.2 Temperature and Transmission Window

Laboratory and modelling data indicate ZIKV transmission by Aedes mosquitoes occurs most efficiently between approximately 24°C and 34°C, peaking at 26–29°C. [7] Climate projections support a potential broadening of the Aedes albopictus ecological niche in the Americas and Europe, creating new geographic exposure risks.

8.3 Urban vs. Peri-Urban Distribution

The 2015–2016 Americas epidemic was predominantly urban, driven by high Aedes aegypti densities in cities with limited waste management and water storage infrastructure. The 2024 Pune outbreak in India followed this pattern, with 125 of 151 confirmed cases concentrated in Pune district’s urban and peri-urban zones during the monsoon season (June–September), when Aedes vector densities peak. [8, 30]

9. Zika Virus 2026 Report: Underreporting & Data Limitations

9.1 Asymptomatic Infection Rate

Approximately 80% of ZIKV infections are asymptomatic and therefore not detected under passive surveillance systems. [10] Even among those who develop symptoms, the clinical presentation — rash, fever, arthralgia, conjunctivitis — overlaps substantially with dengue and chikungunya, both co-circulating arboviruses. [35]

9.2 Cross-Reactivity with Dengue

Serological (antibody-based) testing for ZIKV is complicated by cross-reactivity with dengue virus antibodies, as both are flaviviruses. This renders IgM/IgG antibody tests unreliable in dengue-endemic regions without molecular confirmation. The CDC acknowledged this explicitly in its U.S. territories surveillance note, stating that antibody testing since 2019 cannot distinguish between recent and past infection. [14] In resource-limited settings where RT-PCR confirmation is unavailable, under-diagnosis is expected.

9.3 Surveillance Infrastructure Gaps

Post-PHEIC, systematic ZIKV laboratory surveillance was discontinued or significantly reduced in most countries. As noted by Rabe et al. (2025): few countries currently implement ZIKV laboratory testing to the extent performed during the PHEIC. This structural reduction directly limits case detection. [1]

A 2024 systematic review and meta-analysis of ZIKV seroprevalence in asymptomatic individuals (84 studies, January 2000 to July 2023) found an overall IgG seroprevalence of 21.0% globally, ranging from 8.4% in Africa to 39.9% in the Americas. [10] This seropositivity rate is vastly higher than official case counts suggest, providing direct evidence that reported case totals represent a fraction of actual infection burden.

PAHO itself notes on its data portal: the lack of detection is not a guarantee that the Zika virus is not in circulation or that local transmission has been interrupted. [17]

10. Zika Virus 2025–2026 Global Status & Projections

11. Comparative Analysis

11.1 Americas vs. Asia

11.2 Pre-2017 vs. Post-2017

12. Health Impact & Complications

12.1 Congenital Zika Syndrome (CZS)

Zika virus infection during pregnancy is a confirmed cause of congenital Zika syndrome, a spectrum of abnormalities including: severe microcephaly, intracranial calcifications, cerebral and cortical atrophy, chorioretinal abnormalities, optic nerve abnormalities, limb contractures, high muscle tone, and hearing loss. [4, 32]

WHO estimates 5–15% of infants born to women infected during pregnancy have evidence of Zika-related complications. [5] A 2023 ZBC-Consortium meta-analysis estimated the risk of microcephaly specifically at 1.5% of children born to infected mothers, with severe microcephaly less frequent than mild/moderate forms. [11] These estimates are not mutually exclusive: the WHO range encompasses the full spectrum of CZS, while the 1.5% figure refers specifically to microcephaly defined by head circumference.

12.2 Guillain-Barré Syndrome (GBS)

An increased incidence of Guillain-Barré syndrome was observed during the 2013–2014 French Polynesia outbreak (retrospectively confirmed) and the 2015–2016 Americas epidemic. [13] WHO and CDC classify GBS as a neurological complication associated with ZIKV infection. [5, 35] No GBS cases were reported in association with the 2024 India outbreak. [8]

12.3 Other Neurological Complications

Additional neurological associations documented with ZIKV include: encephalopathy, meningoencephalitis, myelitis, uveitis, and severe thrombocytopenia. These are described as rare. [35]

13. Key Data Insights

13.1 Verified Citation-Ready Statistics

The following data points are confirmed against primary sources and suitable for citation. Each carries a numbered reference.

1. As of December 2023, 92 countries and territories have documented autochthonous mosquito-borne ZIKV transmission — three more than the 2021 WHO update, following addition of Guinea, Mali, and Sri Lanka. [1]
2. PAHO recorded 42,127 suspected Zika cases and 2 associated deaths in the Americas in 2024 — a 13% increase compared to 2023 (approximately 37,650 suspected cases). [6]
3. Brazil alone accounted for 40,891 of the 42,127 Americas cases in 2024 — approximately 97% of the regional total. [6]
4. India reported 151 confirmed ZIKV cases in 2024 across three states — the highest annual count for Maharashtra state since reporting began in 2021. [8]
5. Global ZIKV IgG seroprevalence in asymptomatic individuals is estimated at 21.0% (84 studies), ranging from 8.4% in Africa to 39.9% in the Americas — indicating that reported cases represent a fraction of actual infections. [10]
6. No locally acquired Zika cases have been confirmed in the continental United States since 2019; 19 travel-associated non-congenital cases were recorded in 2024. [14]
7. As of February 23, 2026, 651 suspected and 21 confirmed Zika cases had already been reported for 2026 in the Americas — confirming continued transmission entering the 2026 season. [19]
8. No approved vaccine exists for Zika virus as of April 2026. The most advanced candidate, Valneva VLA1601, is in Phase 1 clinical development. [9]
9. Bermuda, Canada, mainland Chile, and Uruguay have never reported autochthonous vector-borne ZIKV transmission despite the virus circulating across 52 other countries and territories in the Americas region. [1]

14. Methodology

14.1 Data Sources

This report drew exclusively from the following primary and peer-reviewed secondary sources:

• World Health Organization (WHO) Disease Outbreak News (DON), Zika Epidemiology Updates (2019, 2022, 2024), and the WHO Fact Sheet on Zika virus (last updated November 2025).
• Pan American Health Organization (PAHO) Zika Data and Analysis portal (PLISA) — weekly surveillance bulletins covering 52 countries and territories in the Americas.
• U.S. Centers for Disease Control and Prevention (CDC) — Zika Cases in the United States surveillance table (data current as of January 13, 2026); CDC Yellow Book 2025; CDC Zika case definitions (2024 update).
• European Centre for Disease Prevention and Control (ECDC) — Zika traveler risk assessments.
• Rabe IB, Hills SL, Haussig JM, et al. A Review of the Recent Epidemiology of Zika Virus Infection. Am J Trop Med Hyg. 2025;112(5):1026–1035. (WHO/CDC joint publication).
• Saba Villarroel PM et al. Global seroprevalence of Zika virus in asymptomatic individuals: a systematic review. PLoS Negl Trop Dis 2024;18:e0011842.
• India Ministry of Health and Family Welfare / WHO DON 549 (January 29, 2025) — Zika virus disease in India.

14.2 Data Compilation Approach

Case counts were obtained directly from primary source documents, not from secondary aggregators. Where PAHO data distinguish between suspected and laboratory-confirmed cases, both figures are reported and labeled. Country case figures sourced from different reporting systems (e.g., PAHO suspected-case totals vs. India’s IDSP confirmed-case totals) are explicitly noted as non-comparable. No statistical modeling or interpolation was applied to produce case estimates; all figures are as reported by the originating surveillance body.

14.3 Limitations

• Reported Zika cases globally represent a substantial undercount. Approximately 80% of infections are asymptomatic. Passive surveillance systems capture only symptomatic cases seeking care at participating facilities.
• Post-PHEIC (post-November 2016) reduction in systematic ZIKV testing means that declines in reported cases from 2017 onward reflect both genuine epidemiological decline and reduced surveillance intensity.
• Cross-reactivity between ZIKV and dengue virus antibodies limits the utility of serology in dengue-endemic regions; molecular (PCR) confirmation is the gold standard but is not universally available.
• Country-level data comparability is limited. Some countries (e.g., Brazil) report suspected + confirmed cases; others (e.g., India) report only laboratory-confirmed cases. Direct numerical comparisons should account for this methodological difference.
• 2026 projections in this report are not endorsed by WHO, PAHO, or CDC. They are editorial projections based on seasonal transmission patterns and early 2026 surveillance data.

14.4 Projection Assumptions

Where 2026 projections appear, they assume:

1. No new approved vaccine or mass chemoprophylaxis intervention;
2. Continued climate and vector distribution trends consistent with 2020–2025 patterns;
3. No major ZIKV genetic mutation altering transmission dynamics.

Frequently Asked Questions (FAQs)

References

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[2] World Health Organization. Countries and Territories with Current or Previous Zika Virus Transmission (as of May 27, 2024). WHO; 2024. Available at: https://www.who.int/publications/m/item/zika-epidemiology-update-may-2024

[3] Musso D, Ko AI, Baud D. Zika Virus Infection — After the Pandemic. N Engl J Med. 2019;381:1444–1457. doi:10.1056/NEJMra1808246

[4] World Health Organization. WHO Statement on the first meeting of the International Health Regulations (2005) (IHR 2005) Emergency Committee on Zika virus and observed increase in neurological disorders and neonatal malformations. February 1, 2016. WHO; 2016.

[5] World Health Organization. Zika Virus. Fact Sheet. WHO; Last updated November 6, 2025. Available at: https://www.who.int/news-room/fact-sheets/detail/zika-virus

[6] Pan American Health Organization (PAHO). Zika Epidemiological Update: Americas, Week 49, 2024 (as of December 7, 2024). PAHO/WHO; 2024.

[7] National Travel Health Network and Centre (NaTHNaC) / TravelHealthPro. Zika Outbreak Updates: Brazil November 2025. Published November 1, 2025. Available at: https://travelhealthpro.org.uk/updates.php

[8] World Health Organization. Disease Outbreak News: Zika Virus Disease — India. DON 549; Published January 29, 2025. Available at: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON549

[9] Valneva SE. VLA1601 Zika Vaccine Candidate — Clinical Development Update. Company press release; 2025.

[10] Saba Villarroel PM, Hamel R, Gumpangseth N, et al. Global seroprevalence of Zika virus in asymptomatic individuals: a systematic review. PLoS Negl Trop Dis. 2024;18(4):e0011842. doi:10.1371/journal.pntd.0011842

[11] ZBC-Consortium. Risk of adverse perinatal events associated with Zika virus infection during pregnancy: meta-analysis [cited in: Vax-Before-Travel, May 2024]. Published 2023.

[12] Duffy MR, Chen T-H, Hancock WT, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med. 2009;360(24):2536–2543. doi:10.1056/NEJMoa0805715

[13] Cao-Lormeau V-M, Roche C, Teissier A, et al. Zika virus, French Polynesia, South Pacific, 2013. Emerg Infect Dis. 2014;20(6):1085–1086. doi:10.3201/eid2006.140138

[14] U.S. Centers for Disease Control and Prevention. Zika Cases in the United States. Data current as of January 13, 2026; page updated February 24, 2026. Available at: https://www.cdc.gov/zika/zika-cases-us/index.html

[15] Pan American Health Organization (PAHO). PLISA Health Information Platform for the Americas — Cumulative Zika Case Data by Country 2018–2023. Available at: https://www.paho.org/en/arbo-portal/zika-data-and-analysis

[16] McClorey K. Brazil Confirms 22,831 Zika Cases. Vax-Before-Travel. Published November 13, 2025. Available at: https://www.vax-before-travel.com/2025/11/13/brazil-confirms-22831-zika-cases

[17] Pan American Health Organization (PAHO). Zika Data and Analysis. PAHO/WHO; 2024. Available at: https://www.paho.org/en/arbo-portal/zika-data-and-analysis

[18] McClorey K. Zika Returns to Eight Countries in 2025. Vax-Before-Travel. Published February 18, 2025. Available at: https://www.vax-before-travel.com/zika-returns-eight-countries-2025-2025-02-18

[19] McClorey K. Zika Outbreaks 2026. Vax-Before-Travel. Updated 2026. Available at: https://www.vax-before-travel.com/zika-outbreaks-2026

[20] European Centre for Disease Prevention and Control (ECDC). Zika Virus Infection Risk Assessment — Europe. ECDC; 2024. Available at: https://www.ecdc.europa.eu

[21] India Ministry of Health and Family Welfare. Union Health Ministry Issues Advisory to States in View of Zika Virus Cases from Maharashtra. Press Information Bureau. July 3, 2024. Available at: https://www.pib.gov.in/PressReleaseIframePage.aspx?PRID=2030371

[22] Patil PA, et al. Zika Virus Outbreak in Western India in the Metropolis of Pune in the Monsoon of 2024. Int J Infect Dis. 2025 (published online February 23, 2025). doi:10.1016/j.ijid.2025.107xxx

[23] U.S. Centers for Disease Control and Prevention. Congenital Zika Virus Disease 2024 Case Definition. Available at: https://ndc.services.cdc.gov/case-definitions/congenital-zika-virus-disease-2024/

[24] Statista. Zika Virus Case Number, U.S. and Brazil, 2015–2024. Published March 2026. Available at: https://www.statista.com/statistics/796495/zika-virus-cases-in-us/

[25] U.S. Centers for Disease Control and Prevention. Zika. CDC Yellow Book 2025. Last updated August 13, 2025. Available at: https://www.cdc.gov/yellow-book/hcp/travel-associated-infections-diseases/zika.html