Dengue fever is a mosquito-borne infection which presents with sudden onset of a high fever, generalized muscle and/or joint pains and headache. Nausea, vomiting and a rash may also be present.
Transmission occurs during the day (unlike malaria) and many countries around the world have the Dengue viruses. Areas where the disease is endemic include Asia, the South Pacific, the Caribbean Basin, Africa, and Central and South America. Most common areas affected are South-East Asia and tropical South America. There have been five epidemics in north Queensland in the last decade however, because virtually all the cases have been imported, north Queensland is not considered to be an endemic area per se.
There is no vaccine, but the disease is usually self-limiting.
Dengue fever exists in four serotypes or different forms. If a person has been infected by one of the serotypes, they gain immunity to that particular serotype. The immune response to one form of the virus does not protect against the three other forms of the virus. Thus, an immune response to one of the serotypes of Dengue is not protective against being infected by a different serotype.
Secondary dengue infections occur when an individual has developed an immune response to one of the dengue serotypes (by a previous infection) and then he or she contracts another infection by one of the other serotypes.
A complication, secondary infections can, in relatively rare cases, cause a more serious disease called dengue haemorrhagic fever. DHF is found predominantly amongst children and adolescents. While DHF in adults is a serious disease it is more serious for children.
Dengue should be considered in any traveller who has fever and symptoms occurring within three weeks of travel to a tropical area, especially an epidemic area. Because there is no vaccine, travellers must take measures to avoid mosquito bites.