There are four distinct, but closely related, viruses which cause dengue. Recovery from one type of virus provides lifelong immunity against that virus type but provides only partial and transient protection against subsequent infection by the other three. The global prevalence of dengue has grown dramatically in recent decades. The disease is now widespread in more than 100 countries in Africa, America, the Eastern Mediterranean, and with South-East Asia and the Western Pacific being the most seriously affected. Dengue Haemorrhagic Fever is transmitted to humans through the bite of infected female mosquitoes.
Mosquitoes generally acquire the virus while feeding on the blood of an infected person.
Once infected a mosquito is capable of transmitting the virus to susceptible individuals for the rest of its life, during probing and blood feeding. Infected female mosquitoes may also transmit the virus to the next generation of mosquitoes via its eggs. Humans are the main amplifying host of the virus, although studies have shown that in some parts of the world monkeys may become infected and perhaps serve as a source of virus for uninfected mosquitoes. Dengue Haemorrhagic Fever - The Symptoms Dengue haemorrhagic fever is a potentially deadly complication that is characterized by high fever, haemorrhagic phenomena often with enlargement of the liver and in severe cases, circulatory failure. The illness commonly begins with a sudden rise in temperature accompanied by facial flush and other non-specific constitutional symptoms of dengue fever.