Extremadura activates surveillance for the Culex mosquito and the Nile virus

The Extremadura Health Service (SES) and the University of Extremadura (UEx) have formalized an agreement to monitor the Culex genus mosquito and detect the West Nile virus in the region, at a cost of 48,700 euros paid in two installments. The agreement was signed on October 16, 2026, and was published by the Official Gazette of Extremadura (DOE) in issue number 210, dated October 30, 2026, via the Resolution of October 19, 2026, from the General Secretariat (official reference 2026062697, registration RCN202600287).

The agreement was signed by the managing director of the SES, Encarnación Solís Pérez, and the rector of the UEx, Pedro María Fernández Salguero, under Decree 154/2025, of November 18, which regulates conventional activity and the General Registry of Agreements of the Administration of the Autonomous Community of Extremadura. The publication order was signed by the general secretary, David González Gil, from the Vice Presidency and Ministry of Presidency, Coordination of Government Action, Interior, and Emergencies.

The text establishes the term of validity from the date of signing until March 31, 2027, with the possibility of a unanimous extension for up to four additional years. The objective is to implement an entomological surveillance network that determines the distribution and abundance of Culex, activates an early detection system, and incorporates analytical capabilities to identify viral RNA before human cases appear.

From 13 to 39 cases in three years

The agreement justifies the urgency based on the epidemiological evolution of West Nile virus fever in the community:

• 2023: 13 cases (11 confirmed and 2 probable), with an incidence of 1.23 per 100,000 inhabitants.
• 2024: 37 cases (32 confirmed and 5 probable), incidence of 3.51.
• 2025: 39 cases (35 confirmed and 4 probable), incidence of 3.70.

The document states that the territory is in a risk 2 scenario, which requires surveillance to include not only the capture and identification of mosquitoes but also the detection of viral RNA as an early warning system. The initiative provides continuity to the SES Prevention and Response Plan against vector-borne diseases, whose Part I already contemplated collaboration with the UEx in the surveillance of the Aedes mosquito.

Eleven sampling points and traps every fifteen days

The obligations are divided between the two signing parties:

• The SES will select 11 sampling points, chosen by the General Directorate of Public Health with advice from the UEx and based on entomological criteria and vector intervention and control; the location of the points may vary according to surveillance needs.
• The SES will install and replenish the traps on a biweekly basis and transport the captures to the Parasitology Area.
• The UEx, through the Parasitology department of the Faculty of Veterinary Medicine of Cáceres, will perform the taxonomic identification and molecular analysis: separation of non-relevant arthropods, identification of genus and species using taxonomic keys, and grouping into pools of a maximum of 50 mosquitoes classified by species, date, and location, preserved at -80 °C.
• Molecular detection will consist of viral RNA extraction and analysis via RT-PCR, with positive and negative controls.
• The results will be communicated progressively by email to the General Directorate of Public Health, the corresponding Health Directorate, and the health zones.

Two payments of 24,350 euros and final report

The total cost amounts to 48,700 euros, charged to budget application 3901/212D/22706 and fund CAG0000001. The payment is divided into two transfers to the UEx of 50% each:

• 24,350 euros upon the signing of the agreement.
• 24,350 euros by November 30, 2026, after receiving the final captures from the traps installed at the end of November and the taxonomic identification and molecular detection report.

Before March 31, 2027, the UEx will send a final report to the General Directorate of Public Health detailing the actions taken, the global results, and the cost of each. Monitoring is the responsibility of a Monitoring Commission with two representatives from each party, which will meet ordinarily every two months and may do so extraordinarily at the request of any of its members.

Partial non-compliance will require the return of unexecuted amounts and, according to the agreement itself, would paralyze the early detection system of the vector and hinder the immediate adoption of preventive and control measures.

The relevance of the agreement is sanitary and seasonal: Extremadura reinforces, with its own personnel and university support, a system that seeks to anticipate the circulation of the virus in mosquitoes before it translates into human infections, in a context of increasing incidence and sustained risk during the warm months.

Source: Official Gazette of Extremadura, no. 210, of October 30, 2026, section III (Other Resolutions) (official reference: 2026062697).