Health experts are warning travellers to take precautions against being bitten by mosquitoes amid a worldwide increase in dengue fever.
Unlike malaria, for which prophylaxis offering varying degrees of protection is available, there is no immunisation for dengue – and no treatment for those who catch this sometimes fatal disease. The US Centers for Disease Control in Atlanta describes the disease as "resurgent" and reports that last year there were up to 100 million cases worldwide and several hundred thousands cases of its more serious form, dengue haemorrhagic fever.
The only treatment for dengue is rest. Though it is not usually fatal on first infection, there are four strains of dengue and experts believe exposure to more than one strain can lead to haemorrhagic fever, which is fatal in 5 per cent of cases.
According to a new survey of British holidaymakers for Aventis Pasteur MSD, one in five British holidaymakers travels to destinations such as Asia, Africa and Central America without being vaccinated at all. One in three fails to get medical advice before travelling.
Dengue is spread by the aedes aegypti mosquito and is characterised by flu-like symptoms, severe muscle aches and rashes. While malaria mosquitoes bite between dawn and dusk, the dengue species bites during the day. Many people who protect themselves against malarial bites in the evening are risking exposure by wearing T-shirts, shorts and sandals during daylight. Travellers who simply take anti-malarials and are happy to be bitten, believing they are fully protected, may be at even greater risk of being infected by more than one strain of dengue.
Some travel clinics appear to be out of date where it comes to the increased risk of dengue. I have friends heading for a honeymoon in Tahiti who were told not to worry about mosquito bites because French Polynesia is a malaria-free zone. In fact, there have been outbreaks of dengue on Tahiti, and the two most popular islands, Moorea and Bora Bora. I was also told that there was no risk of dengue before a recent visit to Kuala Lumpur, but a cardiologist friend in the city warned that dengue was increasingly common. The aedes mosquito is now firmly established in Asia, South America, East Africa, the South Pacific and even southern parts of the United States and north-eastern Australia.
The Hospital for Tropical Diseases in London confirmed it sees a "fair number" of people returning from Asia with dengue fever. It believes the numbers of Britons who fall ill with dengue are significantly underestimated because many of those who catch it think they simply have a bout of severe flu. "People are much less aware of dengue than of malaria," said Dr Dan Agranoff, specialist registrar in tropical medicine at the Hospital for Tropical Diseases. "People are much more blasé about the need to avoid being bitten. There is a lot more to travel medicine than vaccination and malarial prophylaxis."