Are Mosquitoes A Problem in Portugal?

Mosquitoes are a part of life in Portugal, especially during the warmer months, and many people—particularly those living near still water—notice an increase in bites in summer. Traditionally, mosquitoes have been more of a nuisance than a genuine public health concern. However, recent monitoring by the health authorities shows that one invasive species, the Aedes albopictus mosquito (often called the “tiger mosquito”), is slowly expanding its range within Portugal.

Important 2025 Update

According to the Directorate-General of Health (DGS), the Aedes albopictus mosquito was identified in four new municipalities in 2025:

• Condeixa-a-Nova
• Covilhã
• Lagos
• Portimão

This adds to detections in previous years across parts of the Algarve, Alentejo, Lisbon, Oeiras, Cascais, Porto district, and Vila Verde, among others. While this expansion reflects broader environmental and global mobility trends, experts stress that the situation is not considered alarming.

A leading researcher quoted in the SÁBADO report explains that the detection of this mosquito in Portugal is still relatively episodic and that they do not appear in large numbers. In other words, the species is present—gradually more so each year—but not yet widespread.

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Does This Mean There Is Dengue in Portugal?

The short answer from the SÁBADO article is: No, not on mainland Portugal.

Between 1 January and 9 October 2025, Portugal recorded 37 cases of dengue:

• 35 were imported (contracted abroad and brought into Portugal)
• 2 were local (autochthonous), and both occurred in Madeira, not the mainland

Health authorities stated clearly that there is no evidence of dengue transmission in mainland Portugal, even though Aedes albopictus is present. This may seem surprising, but there is a scientific explanation.

Why the Risk on the Mainland Remains Extremely Low

The article emphasises a crucial point:

Only very specific mosquito species are capable of transmitting viruses like dengue, and the virus must be able to survive, adapt, and remain active inside the mosquito before it can infect a human.

This is a complex biological process. Even if a mosquito species can theoretically transmit dengue, the virus still needs to successfully establish itself inside that specific mosquito population.

According to the expert interviewed:

• Each virus has specific compatibility requirements with each mosquito species.
• The virus must survive inside the mosquito, reach the salivary glands, and remain active long enough to be transmitted.
• The fact that no chains of transmission have been detected on the mainland suggests that these biological conditions have not been met in Portugal.

As he puts it, the Portuguese situation “is not alarming,” especially because there are no ongoing waves of contagion.

Symptoms and Severity of Dengue

The SÁBADO article summarises the symptoms listed by SNS24:

• Fever (typically 2–7 days)
• Headache
• Muscle and joint pain
• Pain behind the eyes
• Vomiting
• Skin rash
• Occasional bleeding

Most people experience a short-lasting, mild illness that does not require specialised treatment. Severe complications can occur in a minority of cases, including pregnant women, elderly people, chronic illness patients, or those with recent head trauma or surgery.

Why the Mosquito Is Spreading

The article notes two main factors:

1. Climate change
   • Warmer temperatures
   • Milder winters
   • Irregular rainfall
     These changes allow invasive species like Aedes albopictus to survive and reproduce more easily.
2. Global mobility
   • Increased travel
   • Low-cost airlines
   • Mosquito eggs transported in luggage or small containers

These conditions help the mosquito establish itself in areas where it previously could not survive.

What This Means If You Live in Portugal

Most of the usual prevention tips still apply:

• Use mosquito repellent when necessary
• Keep windows closed at night or use temporary fly screens
• Remove standing water around your home
• Use plug-in repellents during summer months

And importantly:

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The presence of Aedes albopictus in Portugal does not mean there is dengue transmission on the mainland.

Health authorities reaffirm that, as of 2025, infection risk for mainland residents remains very low, and the expansion of the mosquito is being closely monitored.