Human, entomological, and animal surveillance of the West Nile virus (WNV), measures included in the Comprehensive Vector Surveillance and Control Program for West Nile Fever for 2025 by the Ministry of Health and Consumption of the Andalusian Regional Government, rules out the circulation of the virus in the fourth week of June in the entire Andalusia region.
However, the neighborhoods of El Alquián and Retamar-El Toyo in Almería will remain on alert for two more weeks, as established by the Comprehensive Vector Surveillance and Control Program for the 2025 season, following the detection of virus-carrying mosquitoes by PCR in the sample from June 11. Subsequent samples have not detected the presence of the virus.
Based on the data obtained so far, the Directorate General of Public Health and Pharmaceutical Management confirms that the WNV detected in Almería corresponds to lineage 2, different from the predominant lineage 1 in the western region, and probably associated with a north-south circulation. However, there are no remarkable epidemiological or clinical differences between the two lineages.
No cases have been reported in humans, birds, or equines in the autonomous community this week. In fact, laboratory studies have been conducted to rule out Nile virus infection in a total of 178 users, and all results have been negative.
From the entomological surveillance information provided by the Ministry and the integration of data from the Doñana Biological Station-CSIC, the Mosquito Control Service of the Huelva Provincial Council, and the various provincial councils, with a current total of 136 traps already installed distributed throughout the eight Andalusian provinces, it is confirmed that the circulation of WNV has not been detected in the latest available analyses.
Regarding the mosquito densities observed in the fourth week of June, traps in the municipalities of La Puebla del Río (Dehesa de Abajo, Seville) and Guadalcázar (Córdoba) show a high presence (500-999) of female mosquitoes of WNV-transmissible species, while traps in La Puebla del Río (Brazo del este), Seville province; Campillos, Fuente de Piedra, and Mijas (Málaga); La Carlota and La Rambla (Córdoba); and Andújar, Arquillos, Baeza, Ibros, Linares, and Navas de San Juan (Jaén) and Pinos Puente (Granada) show moderate presence (100-499) of these mosquitoes. The rest of the traps set up in the entire community provide values with low presence of transmitting species. So far, all PCR virus detection results are negative, except for the positive case in Almería reported on June 20.
The traps have been placed in municipalities classified as high Risk Level (NR), either due to a high probability index of WNV circulation or because the municipality’s situation is suitable for early identification of potential virus circulation expansion. The objective is to early detect the increase in transmitting mosquito densities and virus circulation in them, to inform the local administration and have them intensify surveillance, control, and communication actions in their territory, reducing the chances of transmission to humans, as well as having real-time information to anticipate actions (increase health messages to the population, intensify collaboration between involved administrations, etc.).
The criterion used for the location of the traps in the selected territories has been areas where a significant abundance of the four main vector species of the virus is expected before its presence is detected in population centers, i.e., areas with stagnant water with low salinity, green areas sheltering adults, close to those population centers.
Update of the Comprehensive Vector Surveillance and Control Program for WNV
The Ministry of Health and Consumption approved the update of the Comprehensive Vector Surveillance and Control Program for West Nile Fever for the 2025 season last February, with the participation of more than 250 professionals including municipalities, provincial councils, scientific groups, Public Health inspectors, and companies, through meetings held between December and January.
This program establishes that all municipalities in Andalusia are included in some level of risk, and therefore, all of them require virus control, as it was observed in the last season that the transmitting mosquito species (culex) are present throughout the Andalusian territory. These risk levels have been reduced to three (low, medium, and high) to facilitate understanding by all involved parties, including the population, as well as the prevention and control measures associated with each level. In total, Andalusia has 104 municipalities at high risk (after the elevation of Almería’s level), 313 at medium risk, and 368 at low risk.
Currently, Almería municipality is at high risk (after declaring the alert area in two of its population centers) – the only case that has increased its risk level compared to the beginning of the season – along with 16 municipalities in Cádiz province, 11 in Córdoba, four in Granada, 15 in Huelva, seven in Jaén, nine in Málaga, and 42 in Seville.
Follow-up by Public Health
In March, all municipalities were informed of their risk level, and the Public Health inspectors (over 400 deployed throughout Andalusia) contacted them to provide technical advice on the implementation of surveillance and control measures, which should cover the entire year to ensure that mosquito populations are as low as possible when the peak virus circulation season arrives, from June to October.
These agents have conducted 1,341 verifications in a total of 765 municipalities. It has been found that in 136 municipalities at low risk level (37% of those in this situation), a Mosquito Control Plan (PCM) is implemented or some related action has been taken. On the other hand, 105 (29%) municipalities at low risk level adopt appropriate surveillance and control measures.
In municipalities at medium and high risk levels, a total of 292 (70%) have a Municipal Vector Surveillance and Control Plan (PMVCV) or have taken some related action. Additionally, in 239 (57%) municipalities at medium or high risk levels, appropriate surveillance, control, and communication measures are adopted. In 210 municipalities at these risk levels, storm drains and other control points have been reviewed.