Doctors warn of rising mosquito-borne disease risk in southern Spain

Doctors in Spain have warned of an increasing risk of mosquito-borne illnesses spreading in southern regions, as environmental conditions become more favourable for insect vectors and the viruses they carry. While malaria has been eradicated in Spain for decades, experts say that other mosquito-borne diseases are already showing changes in distribution and frequency, and that this trend is expected to continue.

Southern Spain, particularly Andalucía and coastal Mediterranean areas, provides suitable conditions for mosquito populations due to rising average temperatures, milder winters and shifting rainfall patterns. These environmental changes extend the breeding season for mosquitoes and increase the likelihood of survival through the year. In addition, invasive mosquito species have become established across parts of Europe, including Spain, altering the potential for disease transmission.

West Nile virus is now established in Spain

One of the most established mosquito-borne diseases in Spain is West Nile virus. The virus is transmitted mainly by Culex mosquitoes and has been detected repeatedly in both human and animal populations, especially in southern provinces.

Many infections cause no symptoms at all. When illness does occur, it typically begins with fever, headache, fatigue, muscle aches and sometimes a rash. In a small proportion of cases, particularly in older adults or people with weakened immune systems, the virus can progress to neurological disease such as meningitis or encephalitis. These severe forms can be serious and may require hospitalisation, and in rare cases can be fatal.

Dengue and chikungunya remain emerging risks

Dengue fever has also become a concern, although most cases in Spain remain linked to international travel. Local transmission has occurred in limited instances where infected travellers were bitten by local Aedes mosquitoes.

Dengue typically causes sudden high fever, severe headache, pain behind the eyes, joint and muscle pain, nausea and skin rash. Most people recover within one to two weeks, but a small number develop severe dengue, which can involve internal bleeding, organ complications and a drop in blood pressure. Severe dengue is a medical emergency but remains relatively uncommon in Europe.

Chikungunya virus produces a similar initial picture of fever and fatigue but is particularly known for intense joint pain, which can persist for weeks or months after the acute infection. While it is rarely fatal, the prolonged joint symptoms can be disabling in some cases, especially in older adults.

Malaria is not expected to re-establish

Malaria presents a different epidemiological situation. The disease was historically endemic in Spain but was eliminated in the mid-20th century. Although Anopheles mosquitoes still exist in parts of the country, conditions do not currently support sustained transmission.

Malaria symptoms typically include cyclical fever, chills, headache and fatigue. Without treatment, some forms of malaria can become severe and life-threatening. However, in Spain the risk remains primarily linked to imported cases from endemic regions, and early diagnosis and treatment are highly effective at preventing serious outcomes.

Climate change is altering mosquito patterns

Climate change is influencing mosquito ecology in southern Europe. Higher temperatures accelerate mosquito development and can shorten the time required for viruses to become transmissible within the insect. Milder winters may also increase mosquito survival rates, allowing populations to persist for longer periods. However, disease transmission depends on multiple interacting factors, including mosquito density, human exposure and the introduction of infected travellers.

Surveillance systems are expanding

European public health agencies have reported a broader increase in mosquito-borne disease activity across southern Europe in recent years. Spain has strengthened surveillance systems that monitor mosquito populations, test insect samples for viruses and track human infections. These systems are designed to detect early signs of outbreaks and support rapid response measures.

Advice for tourists and expats in southern Spain

Health authorities recommend a set of practical precautions to reduce mosquito exposure. Eliminating standing water around homes is important, as mosquitoes breed in stagnant water found in containers, plant pots, drains and outdoor storage items.

Personal protection measures include using approved insect repellents containing DEET, picaridin or IR3535, and wearing long sleeves and trousers during dawn and dusk when mosquito activity is often highest.

Indoor protection can include window screens, mosquito nets over beds, and air conditioning or fans, which reduce mosquito entry and biting rates. Avoiding outdoor exposure near wetlands, irrigation areas or stagnant water during peak activity hours can also reduce risk.

1. Outlook remains stable for malaria but evolving for viral diseases

At present, experts do not consider malaria likely to return as an endemic disease in Spain. However, mosquito-borne viruses such as West Nile, dengue and chikungunya are already established at low levels and may become more frequent under favourable environmental conditions.

The overall assessment from health authorities is that Spain is not returning to historical malaria patterns, but is instead facing a gradual increase in the relevance of viral mosquito-borne diseases that are already present in the region.