Extreme measures in Catalonia to contain a possible increase in dengue fever

The Generalitat (Catalan Government) is increasing its control and surveillance efforts to "ward off" a possible scenario of more widespread dengue transmission within Catalonia. This is currently a minority occurrence, but climatic conditions and the proliferation of the tiger mosquito could change in the coming years. The Departments of Health, Territory, Agriculture, and the Interior of the Catalan Government presented at a press conference this Friday the coordinated actions they are taking to combat the spread of arboviruses.

These are diseases caused by a group of tropical viruses that are transmitted to humans by mosquitoes, especially the tiger mosquito (which transmits dengue fever and has already colonized 743 Catalan municipalities) and the common mosquito (which can carry the West Nile virus).

The Deputy Director General of Health Surveillance and Emergency Response of the Generalitat (Catalan Government), Jacobo Mendioroz, emphasized this Friday that Catalonia has the "climatic and vector conditions—the mosquitoes that transmit it—" for a virus like dengue to become "autochthonous," meaning that someone can become infected without having left the autonomous community, simply from a mosquito bite. However, the majority of the detected cases are imported, involving people who arrived in Catalonia already infected.

Only 11 cases of autochthonous transmission since 2022

Thus, during the 2022-2024 period, 1,591 suspected cases of arboviruses were reported, of which 564 were laboratory-confirmed; of these, only 2.1% (11 cases) were of indigenous origin. Of all confirmed cases (imported or indigenous), dengue is the most common (93.6% of cases), while chikungunya, Zika, and West Nile virus fever are in the minority: 4.1%, 1.2%, and 1.1%, respectively.

Between 2022 and 2024 (there are no records for 2025 because cases usually occur in August and September), three outbreaks have also been confirmed: two people in Reus (Baix Camp) with West Nile virus fever in 2022, two people with dengue fever in Malgrat de Mar (Maresme), and eight people with the same virus in Vila-seca (Tarragonès) in 2024.

Mendioroz attributes the still low proportion of autochthonous cases to the surveillance and control work carried out by various services within the Generalitat (Catalan government), although he admits that autochthonous transmissions may increase and dengue may eventually become endemic (that is, the disease may become established and transmitted regularly in a given territory).

"We can't get our hopes up; we're not immune, but anything that buys time and prevents new cases each year can delay that scenario."

Jacobo Mendiaroz, Deputy Director General of Surveillance and Emergency Response

Along the same lines, the Secretary of Public Health, Esteve Fernández, stated that "it would be naive to think" that Catalonia will "save them from becoming endemic," but added: "It's not something that's just around the corner."

In this regard, Fernández has emphasized the need for prevention, both from institutions and citizens.

He indicated that mosquito bites should be avoided by wearing long-sleeved clothing, avoiding wet areas, and applying repellent. He also indicated that shallow, standing water should not be left near homes, as this is where mosquitoes lay their larvae.

Control of the tiger or common mosquito

For their part, the Departments of Health, Land, Agriculture, and the Interior are implementing preventive measures, including control of the tiger mosquito and the common mosquito, as well as monitoring birds and horses (the latter can also be vectors of the West Nile virus).

From a human health perspective, Fernández emphasized the importance of going to a health center if symptoms such as malaise, fever, or discomfort are detected after a bite. This is an important step in making a diagnosis and, from there, controlling possible transmission to other people—which would always be through mosquitoes, not person-to-person—and monitoring the environment and insects in the area where the infected person lives.