Tropical diseases are surging in Spain, and climate change is the reason

Spain is facing a growing threat from tropical diseases such as West Nile fever, Crimean-Congo haemorrhagic fever and chikungunya, driven by climate change, which is fuelling the spread of mosquitoes and ticks carrying exotic bicho.

The heat is closing in, and not just outdoors. In Spain, rising temperatures are creating a breeding ground for bicho that we used to see only in documentaries or distant news reports. We are talking about tropical and emerging diseases, and the data from recent years leave no room for doubt: they are soaring.

## Mosquitoes and ticks, the new neighbours

Spain began paying attention to these infections a decade ago, but it was after the pandemic that they truly exploded. The **common mosquito**, for instance, is responsible for **West Nile fever**. Although the first case was recorded in **2010**, it was not until **2020** that cases stopped being isolated incidents and became relatively frequent. The numbers speak for themselves: **20** infections were reported in **2023**, but in **2024** the figure shot up to **159**, and **2025** closed with **45** cases and five deaths. And **2026** is on track to be the second-worst year, with more than **70** cases in western Andalusia and Badajoz alone, including more than **20** hospitalisations and one death. Tyre imports and the presence of wetlands, where mosquitoes breed freely, have turned areas such as Andalusia into an ideal hotspot.

But bicho do not live on mosquitoes alone. The **Crimean-Congo haemorrhagic fever** has the **tick** as its main transmitter. The reservoir is grazing livestock, and if you walk through the countryside with bare legs, ticks can easily latch on. Cases have been recorded every year since **2020**, with peaks of four infections in **2024** and **2026**. Though the numbers may seem small, the disease's fatality rate is alarming, reaching up to **40%**. Initial symptoms resemble a severe flu, but they can develop into serious haemorrhaging and multi-organ failure.

## The rise of chikungunya and the shadow of dengue

The **chikungunya bicho** is another whose cases have tripled compared with last year, reaching **119** in **2026**, all of them imported. But the risk is real: it is already being transmitted in central Europe, and in Spain and Italy the risk of infection lasts more than six months. The **tiger mosquito**, the **Aedes albopictus**, a vector increasingly present in our territory, is to blame. What was once confined to the Mediterranean coast has now spread to almost the whole country. If temperatures keep rising and we keep travelling, its expansion is an ever more likely prospect.

**Dengue** and **zika** are also recurring. Dengue in particular has seen locally transmitted cases in Spain, although so far they have been kept under control. The surge in mass tourism after the pandemic, with Spain quintupling its visitor numbers in just a few years, has made it easier for these bicho to arrive. International trade and goods transport also play a crucial role in the spread of these pathogens.

## A challenge for public health

**Climate change** is the great catalyst behind this situation. Rising temperatures and shifting rainfall patterns are allowing vectors such as mosquitoes and ticks, which previously could not survive or reproduce in Spain, to now do so with ease. Federico Arribas, spokesman for the Spanish Society of Epidemiology, sums it up clearly: "Bicho know no borders".

These diseases, once confined to tropical and subtropical regions, now find a favourable habitat in Spain. Globalisation, international trade and mass tourism, combined with global warming, have created the perfect storm. **Bicho**, for instance, is another example of how we are entering ecological niches where there was previously no contact with humans.

While bicho such as chikungunya or dengue may have a more gradual impact than more explosive respiratory bicho, the challenge for public health is undeniable. Maintaining robust epidemiological surveillance, controlling vector populations and, above all, travelling with common sense are key to preventing greater ills. The situation demands vigilance and precaution, because exotic bicho seem to have settled in for good.