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Zika
A potentially serious infectious disease- Published on: 18/09/2026
- Reading time: 12 min
This report was prepared in collaboration with André Cabié, medical coordinator of the Caribbean Clinical Investigation Center (CIC).Inserm2504), head of the infectious and tropical diseases department at the University Hospital of Martinique and member of the Pathogenesis and control of chronic and emerging infections unit (PCCEI, unit 1058 Inserm/University of Montpellier/University of the Antilles).
Table of Contents
In short
- Zika virus infection is an arboviral disease, a viral illness transmitted by Aedes mosquitoes present in the French overseas departments and regions as well as in 81 departments of metropolitan France. It can also be transmitted sexually.
- A global epidemic occurred in 2015–2016, with hundreds of imported cases in mainland France. Since then, the virus has circulated little worldwide, and only 18 imported cases were recorded in mainland France in 2025.
- Vaccine development is currently hampered by the low circulation of the virus, which makes it difficult to assess the effectiveness of the products developed. However, having a vaccine is essential to protect the population from neurological complications in the event of a new epidemic.
Understanding Zika
Zika virus infection is caused by an arbovirus, a family of viruses that also includes dengue and chikungunya viruses , all three of which are primarily transmitted to humans through female mosquitoes of the genus Aedes .Since its first identification in Uganda in 1947, the Zika virus has spread across the globe due to human migration and the adaptation of the Aedes mosquito to new territories, facilitated by climate change. The virus's pathogenicity may also have evolved over time, with an increase in cases associated with serious complications following successive epidemics.
In 2013 and 2014, a Zika epidemic spread through the Pacific Islands before reaching French Polynesia, where 55,000 cases were reported. Another major global epidemic occurred in 2015–2016, particularly in South America and the Caribbean, during which the Zika virus affected millions of people. Several hundred imported cases were reported in mainland France, originating from Guadeloupe, Martinique, and French Guiana, where the epidemic was raging.
Since 2017, there has been no active circulation of the Zika virus in the French overseas territories. However, it continues to circulate at a low level in endemic countries in Latin America, Africa, and the Asia-Pacific region. In 2025, 18 imported cases were recorded in mainland France, in people who had recently stayed in Thailand, Indonesia, Ivory Coast, Brazil, or Laos. The first autochthonous case—that is, occurring in a person who had not stayed in an area where the virus is known to circulate in the 15 days preceding the onset of symptoms (and who was therefore infected locally)—was observed in 2019 in the Provence-Alpes-Côte d'Azur region. In total, three autochthonous cases were reported that year, but none since. These cases therefore remain exceptional despite the increasing presence of the tiger mosquito ( Aedes albopictus ) in France. The latter is now installed in 81 departments, where approximately 49% of the metropolitan population resides.
Three transmission channels
Vector-borne transmission (via a mosquito) is the most common
The Zika virus is most often transmitted to humans through the bites of female mosquitoes of the Aedes aegypti or Aedes albopictus species, which are themselves infected because they have previously bitten a person carrying the virus . Inhaled along with blood during the bite, the virus multiplies within the mosquito without affecting it and reaches its salivary glands. During a subsequent bite, the mosquito injects saliva and releases the virus into the bloodstream of a new person.An infected person becomes contagious to other mosquitoes one to two days before the onset of symptoms, a period during which the person is said to be "viremic," which corresponds to active circulation of the virus in their blood. They remain contagious for up to about seven days after the first symptoms appear.
Sexual transmission
The Zika virus is also transmitted sexually during unprotected sex. This has been particularly documented in infected men, who can transmit the virus to their partner(s) for several weeks after the onset of infection. However, sexual transmission of the virus by a woman is also possible.Mother-to-fetal transmission
An infected pregnant woman can transmit the Zika virus to her unborn child as early as the first trimester of pregnancy. This transmission, observed in approximately 20 to 30% of cases, can lead to serious brain development abnormalities in the fetus, even though the infection may be asymptomatic in the mother, who may be unaware of her status. Therefore, pregnant women must take strict precautions against mosquito bites in areas where the Zika virus is circulating.Note: The Zika virus can also be transmitted in a medical context, through blood transfusion or in the case of a transplant.
Close monitoring
Monitoring systems for the circulation of the Zika virus exist not only in the overseas departments but also in mainland France.In mainland France, Réunion, and Mayotte, all biologically confirmed cases of Zika virus infection, whether imported or locally acquired, require the physician or laboratory to report them to the Regional Health Agency (ARS). This procedure is mandatory and must be carried out as quickly as possible. Surveillance is particularly active in departments where Aedes albopictus is present from May 1st to November 30th, the mosquito's active period. Each report triggers an investigation and the intervention of a mosquito control team ("vector control") to reduce the risk of local transmission. This is accompanied by communication with healthcare professionals, the public, and the relevant local authorities.
On the other hand, there is no mandatory declaration in the French departments of America (Guadeloupe, Guyana, Martinique, Saint-Martin) because the virus has already circulated actively there.
Symptoms and complications
It is estimated that more than half of people infected with the Zika virus (50 to 60% of cases) show no symptoms . If symptoms do appear, they generally manifest about 5 days after the bite of the mosquito vector (this period can last up to 12 days). These symptoms typically include:- a skin rash (small red bumps) possibly accompanied by itching,
- of a moderate fever (which may be absent),
- of conjunctivitis,
- of fatigue,
- muscle and joint pain,
- headaches and retro-orbital pain (behind the eyes).
Rarely, however, the infection can lead to severe neurological and autoimmune complications , particularly Guillain-Barré syndrome, a disease of the peripheral nervous system that causes paralysis (approximately 24 cases per 100,000 people infected with Zika). These serious complications require prolonged hospitalization.
A risk of fetal malformation
If a pregnant woman contracts the Zika virus, it can be transmitted to the fetus and cause brain development abnormalities, including microcephaly (abnormally small brain size) associated with mental and/or cognitive impairments. If infection occurs during the first or second trimester of pregnancy, the risk of microcephaly is 1 to 13%.Other symptoms have been described in these children: facial disproportion, skin folds due to excess skin tissue ( cutis gyrata ), poor control of muscle activity (hypertonia or involuntary contractions), and irritability. Abnormalities can be detected on brain imaging. In some children, the genitourinary, cardiovascular, and digestive systems may also be affected.
A molecular diagnosis
If you experience symptoms suggestive of a Zika virus infection, you should consult a doctor. Symptoms can appear up to 12 days after leaving an area where the virus is circulating .Diagnosis of the infection relies on blood or urine tests that look for the presence of the virus (detection of its genetic material by RT-PCR), or that ofantibodyspecific tests that recognize it (serology).
Given the risk of potential complications for the fetus, pregnant women should consult a doctor not only if they experience any suggestive symptoms, but also if they have had unprotected sex with someone who has traveled to an area where the virus is transmitted. If Zika virus infection is confirmed, they can be monitored by a multidisciplinary prenatal diagnostic center for close follow-up of fetal development.
Symptomatic treatment
There is no specific antiviral drug to treat Zika. Treatment is purely symptomatic and relies on pain relievers, particularly paracetamol . Hospitalization may be necessary in case of complications, especially neurological ones.In departments where Aedes mosquitoes are present and active, it is necessary to protect oneself from mosquitoes for seven days after the onset of symptoms to avoid transmitting the virus to a mosquito. Since the virus can be transmitted sexually, protected sex should be used from the beginning of symptoms in case of infection and for up to six months after returning from a stay in an area where the Zika virus is circulating.
Preventing infection
There is currently no vaccine against the Zika virus. The only way to prevent infection is to protect yourself from mosquito bites day and night, especially at dawn and dusk, when the insects are most active. It is recommended to use both physical and chemical methods: repellents, long-sleeved clothing, mosquito nets, and insecticide-treated clothing in areas with a high risk of infection.During pregnancy, it is recommended to postpone stays in areas where the Zika virus is transmitted and to have protected sex when the partner has been exposed to the virus.
Prevention also involves vector control to limit mosquito proliferation . To this end, all potential breeding grounds for mosquito larvae (stagnant water) must be eliminated: flowerpots, gutters, used tires, etc. It is recommended to empty any standing water that may accumulate around your home, especially after each rainfall. At the local level, vector control is carried out by public mosquito control operators who spray mosquito breeding sites with insecticides.
The challenges of research
Develop a vaccine
Research into a vaccine against the Zika virus was launched following the 2015 pandemic, primarily due to the serious risk to fetuses if pregnant women become infected and the risk of neurological complications in adults. More than a dozen early-stage, phase 1, and phase 2 clinical trials with different types of vaccines have been initiated.Some vaccine candidates, known as "inactivated" vaccines, are composed of Zika virus particles combined with fragments of other pathogens to induce stronger immunity. Their effectiveness requires several booster doses. Others, known as "live attenuated" vaccines, rely on the use of the active but harmless Zika virus. They have the disadvantage of potentially inducing viral symptoms and are not recommended for immunocompromised individuals. DNA or other vaccines are also being developed.RNA, which rely on the injection of a DNA or RNA sequence encoding a viral protein capable of inducing immunity are also being developed.
The development of vaccines against the Zika virus faces several challenges. The first is the lack of a reliable animal model to assess their safety and efficacy in preventing mother-to-child transmission and protecting fetuses. Furthermore, the absence of active virus circulation worldwide complicates the conduct of clinical trials in humans. To address this, controlled infection trials—that is, the deliberate infection of healthy individuals—can be considered to test vaccine efficacy. One such trial was conducted in the United States in 2021.
Antibodies to prevent the disease and/or its complications
Other projects focus on developing antibodies that bind specifically to the Zika virus to neutralize it. In the event of an epidemic, these antibodies could be administered to prevent infection, particularly in pregnant women or those planning a pregnancy. These neutralizing antibodies could also be used as a treatment to reduce the risk of neurological complications. The goal is to develop monoclonal antibodies with a lifespan of several months in the body, so they can be administered once (by intramuscular injection) when a woman is planning a pregnancy or at the beginning of one. Two of these monoclonal antibodies (Tyzivumab and dMAb-ZK190) are currently in early-stage development (phase 1 trial).New vector control strategies
In addition to the use of insecticides and the reduction of larval habitats, new vector control approaches are being tested to reduce the risk of Zika virus transmission in the event of an epidemic.Infection of Aedes mosquitoes with the Wolbachia bacterium reduces the insects' lifespan and slows viral transmission. A World Mosquito program is underway to test this strategy in a dozen countries: Australia, Brazil, Colombia, Indonesia, Sri Lanka, India, Vietnam, Kiribati, Fiji, Vanuatu, New Caledonia, and Mexico. Infected mosquitoes are released in endemic areas and transmit the bacterium to wild mosquitoes. A 37% reduction in the risk of Zika virus transmission has been observed, but only in certain areas where Wolbachia mosquitoes have been released. However, these data are difficult to interpret given the low circulation of the Zika virus since 2016.
In Réunion, another approach involves releasing sterile males . This is the Optis project, coordinated by the French Agricultural Research Centre for International Development (CIRAD) in partnership with the French Research Institute for Development (IRD). Males are sterilized by irradiation and then released. By mating with wild females, they produce non-viable eggs. Successful trials were conducted in two municipalities in Réunion in 2021, resulting in a drop of more than 90% in mosquito density in one of them. The next step is to demonstrate the effectiveness of this approach on a large scale in an urban area (200 hectares in Saint Joseph in the south of the island). To this end, regular releases are planned until 2027, at a rate of 1,000 sterile males per hectare per week.
Artificial intelligence facilitates this work. Coupled with video, it makes it possible to identify areas with high mosquito density, distinguish the species present, count the populations... The Arbocarto tool, used for several years by the vector control service of the Regional Health Agency of Reunion, serves to model areas with high mosquito density from environmental and epidemiological data, in order to prioritize interventions where the risk of epidemic is highest.
Our content on the same topic
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- October 23, 2025 – Tracking emerging viruses
- July 3, 2023 – Arbovirus: Facing the threat in mainland France
- November 21, 2017 – Sophie Allart, 2017 Innovation Award
Press releases
- January 25, 2023 – Towards a better understanding of the transmission mechanisms of Zika and dengue viruses
- September 7, 2022 – A preclinical study shows the lack of antiviral efficacy of favipiravir against SARS-CoV-2 and its potential benefit against the Zika virus
- May 1 , 2019 – The neurological consequences of the Zika virus finally revealed
- September 11, 2018 – How the Zika virus persists in semen and alters sperm
- March 14, 2018 – Zika: a precise estimate of neurological risks in unborn children
- December 11, 2017 – How the Zika virus induces congenital microcephaly
- January 10, 2017 – Identification of one of the keys allowing the Zika virus to enter brain cells
Also worth discovering
- Dengue – information pack
- Chikungunya – information pack
- Emerging viruses and epidemics – digital exhibition
- What are zoonoses?
To go further
- Zika virus disease– World Health Organization dossier
- Zika– Public Health France file
- Zika– file from the Ministry of Health
- Zika– Pasteur Institute file
Zika · Inserm, La science pour la santé
Le Zika est une maladie infectieuse, provoquée par un virus transmis à l’humain par des moustiques du genre Aedes. Bien que souvent asymptomatique, l’infection peut entraîner des complications neurologiques graves, en particulier des malformations cérébrales de l’enfant à naître en cas de...
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