Flanders reports first five suspected local human cases of West Nile virus

First local human infections identified

Belgian health authorities confirmed on Friday that five people in Flanders are suspected of contracting West Nile virus through local transmission. The probable cases are concentrated in the provinces of Antwerp and Flemish Brabant, located in the corridor between Brussels and Antwerp. Four of the five infected individuals presented neurological symptoms, and one patient remains in the hospital. Additional laboratory confirmation tests are underway, while officials have withheld personal details to protect patient privacy. Sciensano virologist Steven Van Gucht indicated that the appearance of human cases was fully expected following prior animal detections in those same areas.

It was a matter of time. We could expect this at any moment.

Preceding animal cases and transmission dynamics

The human cases follow weeks of active animal surveillance across northern Belgium. According to the Federal Agency for the Safety of the Food Chain (Afsca), approximately 60 infections were detected in wild birds alongside 25 confirmed cases in horses since circulation was first detected in early August. West Nile virus is transmitted to humans and equines via the bite of the common house mosquito, which acquires the pathogen from wild birds acting as reservoirs. The virus cannot spread directly between humans, nor can it transfer from horses to humans or from infected humans back to mosquitoes.

Clinical impact and public health guidance

Public health agencies emphasise that the overall risk of severe illness to the general population remains low. Roughly 80% of individuals infected with West Nile virus develop no symptoms at all. Among the remaining 20%, symptoms are typically mild, including fever, headaches, fatigue, and muscle pain, while severe neuroinvasive disease affects approximately 1% of cases, primarily among elderly or immunocompromised individuals. Departement Zorg spokesperson Anneleen De Sadeleer noted that increased testing and clinical vigilance contributed to identifying these simultaneous cases.

These first infections confirm what earlier findings in birds and horses had already indicated: West Nile virus is currently also circulating in Flanders. That does not mean that Flemings should worry. For most people, the risk of serious illness remains very small.

European context and preventive measures

The Belgian cases coincide with a broader expansion of West Nile virus across Europe during the summer months. Data from the European Centre for Disease Prevention and Control (ECDC) show that recorded human infections across Europe reached 1,086 cases, climbing from 241 cases recorded one month earlier. In response to local findings, the Departement Zorg issued advisories to general practitioners, hospitals, care homes, and assisted living facilities across Antwerp and Flemish Brabant, noting that mosquitoes carrying the virus are active at twilight and overnight. Health officials expect possible further infections until mosquito activity subsides with cooler temperatures and shorter autumn days in October.

It is not really a human virus. It sometimes happens that it is transmitted to humans almost accidentally. It is rather exceptional and generally asymptomatic. Most people do not notice anything. Only a very small percentage develops severe symptoms, including infections of the brain or spinal cord. These people are hospitalised. And a small fraction of them may even die from it. But that remains rare.