The summer season brings with it an increase in the activity of the mosquito that transmits West Nile virus in Andalusia. The Regional Ministry of the Presidency, Health, and Emergencies has declared new areas on alert for the circulation of the pathogen in four municipalities in the province of Seville, bringing the total number of Andalusian towns under intensified surveillance to eleven. So far, two human cases of West Nile fever have been registered, both with mild symptoms, which has activated the control and prevention protocols established by the Comprehensive Surveillance and Vector Control Program.
Early detection of the virus in mosquitoes captured in traps has allowed health authorities to anticipate the risk and take action before further infections occur . The surveillance network, coordinated by the Doñana Biological Station (CSIC), the Seville Provincial Council, and the Regional Government of Andalusia, has been key to identifying outbreaks and defining the areas where intervention is needed. Experts emphasize that public cooperation is essential to reducing mosquito breeding grounds and preventing bites.
Eleven Andalusian municipalities on alert
The General Directorate of Public Health and Pharmaceutical Regulation has placed Gelves, Almensilla, Aznalcázar, and Mairena del Aljarafe on alert after confirming the presence of mosquitoes carrying the virus in traps located near their urban centers. These four towns in the province of Seville join those already on alert: Palomares del RÃo, Constantina, Coria del RÃo, La Puebla del RÃo, Pulpà (AlmerÃa), and Torredonjimeno (Jaén). Additionally, viral circulation was detected in Benacazón, but because the trap was located more than 1,5 kilometers from the town center, it was not deemed necessary to activate the alert.
The declaration of an area on alert lasts a minimum of four weeks, extendable if virus circulation persists. During this period, the affected municipalities must intensify vector control efforts , including adulticide treatments and the elimination of mosquito breeding sites within a 1,5-kilometer radius of residential areas. Information campaigns aimed at encouraging the public to adopt personal protective measures are also reinforced.
Two mild cases of West Nile fever in humans
To date, Andalusia has recorded two human infections with West Nile virus this season. The first case was a woman residing in Seville who spends time in Palomares del RÃo. She was diagnosed by PCR test at the Virgen del RocÃo University Hospital with mild symptoms. The second case, also mild, affected a man from Villamanrique de la Condesa, who began experiencing fever and malaise on July 13 and was confirmed on July 21 by the same hospital.
Health authorities have conducted extensive screening to detect potential infections. A total of 222 individuals and 91 patients with viral meningitis were tested , in addition to 688 blood donors, all with negative results. The virus was also not found in the 208 wild birds analyzed or in equines, indicating that, for now, transmission remains under control in humans.
Entomological surveillance and vector control
The surveillance network in Andalusia has around one hundred traps distributed throughout the provinces to monitor mosquito density and the presence of the virus. Public health officials have carried out more than 1.200 checks in 612 municipalities, inspecting storm drains and other control points. Data from the last week shows a high density of transmitting female mosquitoes in towns such as Palomares del RÃo, Los Palacios y Villafranca, and La Puebla del RÃo, requiring continued vigilance.
The main vectors of the virus in the Iberian Peninsula are mosquitoes of the genus Culex, especially Culex pipiens and Culex perexiguus . These species breed in stagnant water and are responsible for transmitting the pathogen from birds, which act as natural reservoirs, to mammals, including humans. Surveillance is maintained throughout the year, although it is intensified during the warmer months, when mosquito activity is higher.
Recommendations for preventing bites
In the absence of a vaccine for humans, the best strategy to avoid West Nile fever is to protect oneself from mosquito bites . Authorities recommend using approved insect repellents according to the manufacturer's instructions, wearing long-sleeved, light-colored clothing, especially at dawn and dusk, and installing mosquito nets on doors and windows. It is also advisable to avoid the accumulation of stagnant water in flowerpots, buckets, gutters, and other containers, as these are the primary breeding grounds for mosquitoes.
The Andalusian Regional Government has launched community initiatives and information campaigns that have reached more than 50.000 people, and reiterates that prevention is a shared responsibility between government agencies, healthcare professionals, and the public. If you experience fever, severe headache, or neurological symptoms after a bite, you should go to a health center for early evaluation.
With eleven municipalities on alert and two mild cases confirmed, the situation in Andalusia remains under control, but authorities insist on not letting their guard down. The combination of active surveillance, vector control, and personal protective measures has so far contained the spread of West Nile virus, with no severe forms of the disease reported. Summer is not yet over, and everyone's cooperation will be key to keeping the transmitting mosquito at bay.
