Zika Outbreaks

Zika Outbreaks December 2025

Zika virus disease (ZIKV) was first recognized in Uganda in 1947, with the initial human infection confirmed in 1952. In 2016, the World Health Organization (WHO) declared the Zika virus epidemic a public health emergency of international concern. Since then, Zika outbreaks have been reported in tropical Africa, Southeast Asia, the Pacific Islands, in the Americas, and continue to occur in 92 countries and territories globally. The WHO published a Global Strategic Preparedness, Readiness, and Response Plan for Aedes-borne arboviruses on January 20, 2025. Studies predict that because of virus-carrying mosquitoes expanding into new geographic areas, about 1.3 billion people could be impacted by Zika by 2050.

As of 2025, the U.S. Centers for Disease Control and Prevention (CDC) Yellow Book states that international travelers with suspected Zika infection should be tested with real-time polymerase chain reaction or an NS1 antigen test. In 2025, public health and commercial lab testing services can detect Zika infections in people.

Zika in the United States

As of 2025, the Pan American Health Organization (PAHO) reported travel-related Zika cases in the United States. The Hawaiʻi Department of Health announced on May 27, 2025, that it is investigating two travel-related Zika cases, and Puerto Rico has been categorized as having a risk of Zika transmission for several years. As of December 31, 2024, the U.S. CDC reported 19 non-congenital Zika cases among U.S. residents (1 imported case in Texas). In 2023, the CDC reported five non-congenital cases among U.S. residents and 27 in U.S. territories. The CDC says Zika-spreading mosquitoes are found throughout Puerto Rico, where the Department of Health says 16 cases were reported in 2024.

Zika Outbreaks in The Americas

The PAHO has confirmed local transmission of the Zika virus in 52 countries and territories in the Americas since 2015. As of December 2025, over 25,800 Zika cases and four related fatalities were reported in the Americas this year. The PAHO reported 42,127 ZIka cases and two associated fatalities in the Americas in 2024, with the highest proportion of Zika cases reported in Argentina, Brazil, Bolivia, Colombia, and Costa Rica. The PAHO reported over 37,659 Zika cases in the Americas in 2023. In 2021, the U.S. CDC removed its Level 2—Practice Enhanced Precautions notice regarding Argentina's Zika outbreak.

Zika in Europe

The European Centre for Disease Prevention and Control (ECDC) says the Zika virus is not endemic in mainland Europe. In August 2025, France reported four travel-related Zika cases. In November 2024, Italy reported 7 imported Zika cases this year. On September 11, 2024, France reported five imported cases of Zika in 3 departments colonized by Aedes albopictus. In 2022, the European CDC reported that 31,453 Zika patients were confirmed in 13 of 52 countries and territories. In addition, the WHO reported in 2019 that French authorities confirmed an autochthonous Zika virus case in Hyeres, Var department.

Zika United Kingdom

Zika virus disease cases also decreased to 4 cases in the first half of 2025. Zika cases increased to 16 in England, Wales, and Northern Ireland in 2024, up from 8 in 2023. Thailand (5 cases) and Singapore (2) were the most frequently reported travel countries. The UK Health Security Agency (UKHSA) issued a warning on March 21, 2024, concerning Zika outbreaks. Travel-related Zika cases in the UK peaked in 2016 with 725 cases.

Zika Virus Infection Impact

According to the WHO, there is scientific consensus that the Zika virus is transmitted to people by mosquitoes of the genus Aedes. Since 2013, 31 countries and territories have reported cases of congenital microcephaly and other central nervous system malformations associated with Zika virus infection. The WHO reports that Zika virus lineages, the African lineage and the Asian lineage, have recently spread in the Pacific and the Americas. Zika infections can cause microcephaly, Guillain-Barré syndrome (GBS), and other central nervous system malformations. Although the Zika outbreak in southern Brazil has slowed in recent years, live births with microcephaly continue to be reported.

The U.S. CDC published Research, Volume 30, Number 2—February 2024: a temporal phylogenetic analysis revealed limited within-host diversity among most ZIKV-persistent-infected associated samples. The researchers detected unusual viral diversity, uncovering the existence of divergent genomes within the same patient. During pregnancy, healthcare providers can monitor the fetus for signs of congenital Zika virus infection.

An Original Investigation published by JAMA Public Health on January 23, 2025, found that children younger than 5 years born with congenital Zika syndrome (CZS) had a 13.10-fold higher hazard of death compared with those without CZS. The cause-specific mortality hazard ratios were 30.28 for respiratory diseases, 28.26 for infectious and parasitic diseases, and 57.11 for nervous system diseases. Research published in Communications Biology and the Liverpool School of Tropical Medicine on January 20, 2025, reported that the Zika virus hijacks the skin of its human host to send chemical signals that lure more mosquitoes to infect and spread the disease further.

Congenital Zika Syndrome

A population-based study of mortality rates among children younger than 5 years old in Brazil, published in JAMA Network Open in January 2025, showed that children with congenital Zika syndrome (CZS) had a 13-fold higher risk of death compared with those without CZS.

The 2015–2016 ZIKV outbreak in the Region of the Americas revealed the ability of ZIKV from the Asian lineage to cause congenital disabilities, generically called CZS, which caused severe congenital disabilities of the brain and eyes, including severe microcephaly. A study published in Pediatrics in January 2025 concluded that children exposed to ZIKV in utero, even without CZS, demonstrate a greater risk for neurodevelopmental delay in early childhood, with the timing of maternal infection being a significant predictive risk factor. The International Journal of Infectious Diseases published a study in 2025 showing that children with CZS are more likely to experience frequent hospitalizations in early childhood. Scientists have reported that ZIKV RNA is detectable in the semen of infected men for months and is found in newborn children.