A primary case of West Nile virus appeared in mid-July within the Provence-Alpes-Côte d’Azur area, reviews the French Public Well being Company in a weekly report revealed Wednesday, July 30, 2025. Listed below are 4 issues to learn about this virus.
1. Transmitted by mosquitoes and carried by birds
West Nile virus is transmitted to people by mosquitoes of the genus Culex, a species distinct from the tiger mosquito. Mosquitoes turn out to be contaminated by biting contaminated birds. The latter “represent the standard reservoir of the virus and act as amplifying hosts,” notes the Ministry of Well being.
Extra not often, the virus may be transmitted via merchandise of human origin, reminiscent of blood transfusions or organ, tissue, or cell transplants. Circumstances of transmission from mom to baby throughout being pregnant, childbirth, and breastfeeding have additionally been noticed, the ministry provides.
2. Issues in lower than 1% of circumstances
Whereas nearly all of circumstances are asymptomatic, 20% of contaminated folks expertise a flu-like sickness (fever, complications, physique aches). Neurological issues happen in lower than 1% of circumstances, significantly in immunocompromised or aged people, and might result in loss of life.
The virus poses a higher danger to horses, whose mortality charge is taken into account “important” by the Pasteur Institute.
3. International unfold
First detected in Uganda, Africa, and within the West Nile area—from which it takes its identify—in 1937, the virus has since unfold all through the African continent, the Americas, the Center East, and Asia. The primary circumstances in Europe had been recorded within the Sixties, with circumstances detected within the Camargue area in mainland France in 1962 and 1963.
First detected within the Mediterranean basin, its unfold has been confirmed in France, with human and equine circumstances detected on the Atlantic coast and in Nouvelle-Aquitaine. In 2024, the Pyrénées-Atlantiques division was affected by contamination for the primary time.
Local weather change is without doubt one of the causes of the virus’s unfold, as rising temperatures favor the presence of mosquitoes that carry the illness.
