Pathogen and transmission
Dengue is a viral disease which is spread by infected mosquitoes of the Aedes genus, primarily by the Aedes aegypti yellow fever mosquito but also by the Aedes albopictus Asian tiger mosquito. There are four serotypes (substrains) of the dengue virus.
Pathology
Dengue will generally develop four to seven days (in rare cases three to 14 days) after infection by an infected mosquito. In 40 to 80 per cent of cases, the infection will progress with no symptoms at all. But dengue can result in any of a wide range of clinical manifestations. Classic dengue will tend to cause a high fever, headaches, muscle pains and skin rash. In some rare cases – known as dengue haemorrhagic fever or dengue shock syndrome – severe developments have been reported. A second dengue infection poses a higher risk of severe dengue developing.
There is currently no effective medication for dengue, so treatment is focused on addressing the symptoms of the disease. Aches and pains can be eased with fever-reducing and analgaesic medications; but salycilate-based medications should be avoided in view of their blood-thinning effects.
Distribution and frequency of occurrence
The numbers of cases of dengue have risen steeply worldwide in the last few years. The disease has also spread geographically. A few isolated cases of dengue transmission have been seen in Europe, too.
The global increase in dengue infections is reflected in the numbers of cases reported in Switzerland among travellers returning from dengue-endemic regions. No case of dengue transmission within Switzerland has yet been recorded.
At the same time, the numbers of Aedes mosquitoes brought into Europe are growing in Switzerland, too. The Asian tiger mosquito has already established itself in many parts of the country. And the Aedes japonicus Asian bush mosquito is also now found in certain Swiss regions. This species has also proved capable, under laboratory conditions, of carrying the dengue virus. So there is some risk of dengue transmission in Switzerland; but this risk is very small, and is only likely under certain conditions: for such transmission to occur, for instance, a mosquito capable of carrying the virus would have to first bite a dengue-infected person and then pass the virus on to another individual.
Prevention
Any place where dengue is endemic carries the risk of dengue infection. Two anti-dengue vaccines are currently available in Europe, but neither of these is yet approved in Switzerland. The indication for these vaccines is limited to travellers to region in which dengue is endemic, and even then the vaccines are only recommended under certain circumstances (such as the risk of a second dengue infection). At present, the best advice for travellers to dengue-endemic regions is to protect themselves against mosquito bites – by wearing long-sleeved clothing and loose-fitting garments sprayed with insecticide, applying mosquito repellent during the day and in the evenings and sleeping under a mosquito net.
For further information on the global distribution of dengue and ways and means to avoid dengue virus infection, consult your GP or a doctor specialising in travel medicine (see also the HealthyTravel website).