Dengue Fever has been in the news following two cases linked to travel to the Spanish island of Ibiza. This has sparked concerns about the spread of mosquito-borne illnesses in Europe, which is especially unusual for this time of year.
Dengue fever is a viral infection transmitted by the Aedes mosquito, which is found in tropical and subtropical regions worldwide. With rising temperatures and changing climates, there is a risk of mosquitoes and other disease vectors spreading to new areas, potentially causing outbreaks of diseases such as dengue fever.
The two cases of dengue fever in Ibiza were reported by the Spanish Ministry of Health and were both in residents of Germany who had visited the island before becoming ill. Each case was accompanied by two family members who were also suspected to have had dengue fever.
The risk of dengue fever in Spain is highest between the months of May and November, when mosquitoes are most active so to have cases at this time of year is uncommon.
So, why are we seeing cases outside of the usual infection months?
The reason is multi-facetted.
Our medical director and travel health specialist, Dr Richard Dawood explains:
“Firstly, there is the introduction or spread of mosquitoes to “pastures new” – places that might have been previously inhospitable, perhaps through temperature; or alternatively, that offer an environment with plenty of suitable breeding sites that they are suddenly able to take advantage of. These mosquitoes can bring disease with them, or can spread it around if there is a reservoir in the local population.
Secondly, there is the possibility of introducing disease to a vector population that is already established, ready and waiting. This is exactly the (long-standing) concern with yellow fever. There are mosquito species in Asia, for example, that are easily capable of spreading yellow fever were it to be introduced by an infected traveller – which is why Asian countries are so careful to insist on proof of yellow fever vaccination from travellers arriving from the endemic zones of Africa and South America. Asia is yellow fever-free, and wants to remain so. However, this type of introduction has already recently happened in Australia, where Japanese encephalitis (a virus infection that can cause rare but serious complications in humans) has recently established a reservoir of infection in farm animals, that may be impossible to reverse. It is also happening with Lyme disease spreading gradually into parts of Europe (and the UK) with a susceptible tick population.
Similar concerns apply to Zika – there is very large potentially susceptible mosquito population that could spread the virus in many tropical countries, if introduced; dengue fever; and also potentially malaria, in parts of the world that have been the target of successful elimination campaigns, but where mosquito populations could still spread it, were it to be reintroduced, if control measures are neglected or ceased.
With changing climates, a valid concern about global warming is that it could create conditions in which populations of mosquitoes and other vectors thrive and spread – hence the crucial importance of vigilance, surveillance, and early action if needed.”
How can you protect yourself from Dengue Fever?
There is no vaccine against dengue licensed in the UK, though several candidate vaccines are in development.
The best way to protect yourself against dengue fever is to take measures to avoid mosquito bites. This includes wearing protective clothing, using mosquito repellent, and staying in places with air conditioning or screens on windows and doors.
If you develop a high fever during or after travelling to an affected area, seek medical advice as soon as possible and provide details of your recent travel history. Dengue is often also accompanied by a rash and joint or muscle pain.
In conclusion, rising temperatures and changing climates have the potential to create conditions in which populations of mosquitoes and other disease vectors thrive and spread. It is crucial for public health authorities to remain vigilant and take early action if needed to prevent the spread of diseases such as dengue fever. By taking appropriate measures to protect against mosquito bites, travellers can reduce their own individual risk of contracting dengue as well as other insect-borne infections.
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