Tropical diseases are illnesses caused by pathogens that are more common, widespread and found in subtropical and tropical areas.¹ Tropical disease, similar to most diseases, can spread through organisms through transmission methods such as airborne, person-to-person, sexual contact, consumption of contaminated food and water, and intermediate carriers like insects or animals.² Common examples of tropical diseases include cholera, malaria, yellow fever, dengue and Chagas disease.³

In recent years, there has been a known increase in the cases of vector-borne vector disease. Particularly, the UK Health Security Agency (UKHSA) states that there were 2000+ cases of imported malaria to Wales and Northern Ireland in 2023.⁴ This is the highest recorded incidence in twenty years. In this article, we are going to discuss possible reasons for the surge of tropical disease in the UK and Europe. 

Tropical diseases, in the past, were mainly found in tropical and sub-tropical areas such as sub-Saharan Africa, South Asia, Southeast Asia and tropical regions of the Americas.⁵ However, in recent years, tropical diseases have been reported in the UK and Europe in the form of vector-borne diseases. Vector-borne diseases, like malaria, West Nile, Zika, dengue and chikungunya viruses and schistosomiasis⁶ are carried by vectors like ticks, mosquitoes, and insects, who are infected with the responsible pathogens (bacteria, parasites and viruses).⁴ These diseases have been moving further north in recent years. This is mainly due to factors such as globalisation and climate change, allowing the perfect opportunity and environment for vectors to reproduce and spread around the world to regions they were not previously common to. Tropical diseases, carried by these vectors, therefore have spread all across the globe.

History of tropical disease⁵

There is a long history of tropical diseases in humans. There are records of malaria dating back to the Roman times. Additionally, molecular analysis of Egyptian mummies showed samples of malaria, proving the presence of malaria in ancient Egypt.

Despite the early existence of tropical disease, the classification of it only appeared in the 19th century as Americans and Europeans colonised tropical and subtropical countries. Additionally, as the slavery of indigenous tropical and subtropical populations occurred, Europeans came into contact with infectious diseases local to the area. This caused the acknowledgement of tropical diseases in the Western medical sphere. This also led to the development of tropical medicine. Diseases like malaria and yellow fever were some of the first tropical diseases to be studied. In the late 19th to 20th century, vectors and other transmission methods were identified as the medium of infection. The bacteria, virus, or parasite causing the tropical disease was also later identified, especially once the general scientific consensus switched from the miasma theory of disease to the germ theory of disease. The study of tropical diseases also allowed increased control of diseases such as cholera, dengue, and meningitis.  

In modern times, the cases of tropical diseases have grown. This is caused by human migration, tourism, globalisation, a growth in population, lack of public health infrastructure and global warming. This caused controlled diseases to reemerge. New diseases such as ebola also developed, leading to significant public health threats and crises.  

Historically, vectors spread around the world via ship trade routes. For example, a more infectious form of malaria caused by a more effective vector was introduced from Kenya to Brazil in the 1930s,⁷ causing severe malaria outbreaks in Brazil. 

Climate change and tropical disease

Climate change refers to the shift in global temperature and weather patterns. It is known that human activities have been the main driver of climate change since the Industrial Revolution as coal, oil, and fuel are burned and used. This generates greenhouse gases such as methane and carbon dioxide which become trapped in the Earth’s atmosphere. This causes warm air to be trapped in the Earth, thus increasing the Earth’s temperature. 

In Europe, one of the main tropical diseases that is spreading rapidly is malaria. The disease is caused by parasites as they spread to humans through mosquito bites. This causes the infected patient to fall sick with high fever and chills. Malaria is common in tropical and subtropical areas.⁸

Mosquitoes thrive at temperatures higher than 26°C as they are cold-blooded and are incapable of regulating their body temperature. This allows mosquitoes to be active all year in tropical areas.⁹ The increase in temperature in the UK and Europe in general caused by climate change allows the perfect environment for mosquitoes to survive and thrive. Additionally, the wet British weather alongside the warm environment allows mosquito larvae to survive, increasing the number of mosquitoes in the UK. Fortunately, the UK does not currently have significant populations of the species of mosquito that carries malaria despite the overall increase in mosquito populations in the UK.

Besides malaria, mosquitoes can also carry dengue fever. It is known that dengue fever, due to the increase in mosquito population, is becoming a threat in southern Europe and America. 

It is predicted that 500 million more people could become exposed to chikungunya and dengue as these diseases spread to new geographies due to warmer climates. By 2080, this figure could double to 1 billion people.¹⁰

Globalisation and the spread of diseases 

Infection diseases like tropical diseases are known to spread around the world at rapid speeds due to globalisation and the flow of the human population around the world. Examples of diseases that spread around the globe due to globalisation include COVID-19, the 2003 SARS coronavirus outbreak, the 2009 swine flu, the 2013–2016 Ebola virus disease epidemic, and the 2015 Zika virus outbreak. These diseases have caused public health crises around the world in multiple countries.¹² Since the 2000s, the number of people travelling by air has doubled, indicating an increasing number of people travelling globally and an increase in global connectivity. Pathogens can therefore circulate through air transport of humans (and animals). In global pandemics like SARS-CoV-2, it is common for pathogens to undergo genetic modifications as they spread around the world.

By tracking the genetic component of pathogens by genetic analysis, we can trace how widespread these pathogens are. For example, SARS-CoV-2 shows genetic data from the Middle East, California and Brazil. This shows that the connectivity of the world allows the quick spread of diseases around the world. Possible tropical diseases that spread from human to human, like dengue fever, and leishmaniasis may go undetected by border authorities, causing the spread of tropical diseases in the UK and Europe. 

In most vector-borne tropical diseases, international travel introduces new vectors or pathogens into other regions that have a habitable environment. Combined with global warming, the UK and Europe become an ideal location for the spread of vector-borne disease. Vectors are mainly brought into Europe by ships. Locations like water-holding tyres are prime habitats for mosquitoes to be transported.¹³ As the climate of the earth gets warmer and as international shipping increases, it is much more likely that vectors will be transported in international packages through ships, allowing the further spread of tropical diseases. Although vectors are less likely to survive via air travel, “airport malaria” cases have been increasing recently as malaria is spread in international airports.¹⁴ With the worsening climate change crisis, these airport malaria cases will likely increase around the world.

Prevention and control measures

Prevention of vectors

As mosquito species and other vectors that carry tropical diseases enter the UK through the transportation of goods, governments and border control agencies must check packages that may contain potential invasive vectors.

Standing water is known to be the prime environment for mosquitoes to reproduce and for mosquito larvae to survive.¹⁵ It is therefore important to reduce the breeding ground for vectors by clearing stagnant water sources like blocked drains and rainwater bins. Pest control through insecticides reducing breeding grounds is also essential. For the public, it is also important to remove any source of stagnant water use mosquito repellents and wear long-sleeved clothing in mosquito habitats.⁴

Prevention of pandemics

To prevent massive tropical disease pandemics, health organisations and the government should carry out public health surveillance to monitor and potentially predict the changes in disease patterns. The prediction can allow existing health infrastructure to be improved, preventative vaccine research to be done, and funding to be effectively allocated.¹⁰

What we can do as individuals

As individuals, if we experience any symptoms of tropical diseases like malaria, it is important to seek medical attention as soon as possible as these diseases are often considered medical emergencies and can be deadly. Before travelling to countries that have endemic tropical diseases, it is important to seek pre-travel advice about how to avoid vectors, get vaccinated and get educated on the symptoms of different tropical diseases.¹⁶

What we can do to prevent climate change

A significant cause of the quick rise of tropical diseases is due to climate change and the release of greenhouse gases. We must work together as a human race to reduce carbon emissions and hopefully slow down the extent of climate change. Governments should establish stricter rules and regulations on greenhouse gas emissions and punish companies that exceed the limit. The UN and EU should employ more regulations to ensure lower pollutants in the future. As individuals, we could also try to reduce waste to reduce our carbon footprint.

Summary

As globalisation increases and climate change worsens, the UK and other European countries are at risk of tropical diseases that could be deadly. In order to prevent a widespread pandemic, governments should monitor these diseases and put out measures to prevent them. It is also important for civilians, especially those who are travelling to tropical countries, to be educated on the symptoms and dangers of these diseases so the public can seek medical attention as soon as possible. It is also important that we work together as humans to prevent climate change and therefore reduce the likelihood of massive tropical disease pandemic killing millions.