Dengue (pronounced den-ggee) also graphically described by the term "breakbone fever," is one of the top public health problems in the tropical world. Epidemics of dengue have been known since the end of the last century but the spread of the disease following the migration of the mosquito carrier along trade routes from Africa to India thence to S.E.Asia & the Pacific (including tropical Australia) & more recently to Cuba, the Caribbean & South America has accelerated rapidly recently. A rapid rise in urban populations is bringing ever greater numbers of people into contact with the vector (carrier) mosquito, while poor sanitation & lack of adequate resources for water storage & waste disposal provides more opportunities for mosquito breeding. A serious & frequently lethal complication, dengue haemorrhagic fever (DHF) was first recognized during the 1950s & is today a leading cause of childhood deaths in many countries.
There are four distinct viruses which cause dengue, & infection by one does not offer protection against subsequent infection by the other three. Indeed, there is good evidence that infection by a second dengue virus increases the risk of more serious disease. An effective vaccine would have to produce antibodies to all four viruses & the problem has not yet been solved.
HOW THE DISEASE IS TRANSMITTED
Dengue is transmitted by the bite of infected mosquitoes of the Aedes genus. Humans are the main host of the virus, although in some parts of the world monkeys may become infected & act as a reservoir of infection.
The time between infection & illness is only a few days. Fever develops abruptly, may be very high causing convulsions in susceptible infants, & lasts from 3-10 days. The headache is severe & nausea & vomiting are common in the early stages. A characteristic fine red rash occurs frequently but by no means always & differentiation from other causes of fever may be difficult. Almost everyone recovers although often with post-dengue fatigue & muscle wasting. Minor bleeding - nose bleeds, bleeding gums & even mild vomiting of blood - may occur in the course of simple dengue but does not mean that the disease is Dengue Haemorrhagic Fever. This complication with severe illness & serious bleeding & shock is potentially fatal. It is usually found in indigenous children but adults & non-residents do get it albeit rarely.
PREVENTION & CURE
There is no specific cure. Paracetamol rather than aspirin is best for pain & fever & fluid intake is important. In more severe cases where vomiting persists or where there is bad bleeding or shock hospitalisation will be needed. There is no vaccine. Personal prevention is based on measures to avoid mosquito bites: repellents, nets, insecticides. Public prevention involves insecticide "fogging" - not popular in an era of eco-consciousness - & elimination of breeding sites. Aedes mosquitoes breed in very small collections of water such as may be contained in an empty can, a half coconut shell, a discarded motor-car tyre, the base of a pot plant, a blocked roof gutter or even in a tree hollow or leaf axil Public education is vital to the success of any public health campaign & the prevention of dengue epitomises this principal. The educated expatriate can in this respect become a positive asset to the host community.
While dengue vaccines are now on the horizon, they will not be in commercial distribution for a couple more years.