aj avian flu, aj prasaciu chripku, a zaroven dengue fever, neviem ako sa to vola po slovensky.
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Fact sheet N°117
March 2009
Dengue and dengue haemorrhagic fever
Key facts
•Dengue is a mosquito-borne infection that causes a severe flu-like illness, and sometimes a potentially lethal complication called dengue haemorrhagic fever.
•Global incidence of dengue has grown dramatically in recent decades.
•About two fifths of the world's population are now at risk.
•Dengue is found in trop***l and sub-trop***l climates worldwide, mostly in urban and semi-urban areas.
•Dengue haemorrhagic fever is a leading cause of serious illness and death among children in some Asian countries.
•There is no specific treatment for dengue, but appropriate medical care frequently saves the lives of patients with the more serious dengue haemorrhagic fever.
•The only way to prevent dengue virus transmission is to combat the disease-carrying mosquitoes.
Dengue is a mosquito-borne infection that in recent decades has become a major international public health concern. Dengue is found in trop***l and sub-trop***l regions around the world, predominantly in urban and semi-urban areas.
Dengue haemorrhagic fever (DHF), a potentially lethal complication, was first recognized in the 1950s during dengue epidemics in the Philippines and Thailand. Today DHF affects most Asian countries and has become a leading cause of hospitalization and death among children in the region.
There are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that virus but confers only partial and transient protection against subsequent infection by the other three viruses. There is good evidence that sequential infection increases the risk of developing DHF.
Global burden of dengue
Related links
:: Dengue/dengue haemorrhagic fever
:: Dengue haemorrhagic fever: diagnosis, treatment, prevention and control
:: Dengue (Special Programme for Research and Training in Trop***l Diseases, TDR)
The incidence of dengue has grown dramatically around the world in recent decades. Some 2.5 billion people – two fifths of the world's population – are now at risk from dengue. WHO currently estimates there may be 50 million dengue infections worldwide every year.
In 2007 alone, there were more than 890 000 reported cases of dengue in the Americas, of which 26 000 cases were DHF.
The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-east Asia and the Western Pacific. South-east Asia and the Western Pacific are the most seriously affected. Before 1970 only nine countries had experienced DHF epidemics, a number that had increased more than four-fold by 1995.
Not only is the number of cases increasing as the disease is spreading to new areas, but explosive outbreaks are occurring. In 2007, Venezuela reported over 80 000 cases, including more than 6 000 cases of DHF.
Some other statistics:
•During epidemics of dengue, infection rates among those who have not been previously exposed to the virus are often 40% to 50%, but can reach 80% to 90%.
•An estimated 500 000 people with DHF require hospitalization each year, a very large proportion of whom are children. About 2.5% of those affected die.
•Without proper treatment, DHF fatality rates can exceed 20%. Wider access to medical care from health providers with knowledge about DHF - physicians and nurses who recognize its symptoms and know how to treat its effects - can reduce death rates to less than 1%.
The spread of dengue is attributed to expanding geographic distribution of the four dengue viruses and their mosquito vectors, the most important of which is the predominantly urban species Aedes aegypti. A rapid rise in urban mosquito populations is bringing ever greater numbers of people into contact with this vector, especially in areas that are favourable for mosquito breeding, e.g. where household water storage is common and where solid waste disposal services are inadequate.
DengueNet: WHO surveillance
Transmission
WHO/TDR/Stammers
Dengue viruses are transmitted to humans through the bites of infective female Aedes mosquitoes. Mosquitoes generally acquire the virus while feeding on the blood of an infected person. After virus incubation for eight to 10 days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus for the rest of its life. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission, but the role of this in sustaining transmission of the virus to humans has not yet been defined.
Infected humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. The virus circulates in the blood of infected humans for two to seven days, at approximately the same time that they have a fever; Aedes mosquitoes may acquire the virus when they feed on an individual during this period. Some studies have shown that monkeys in some parts of the world play a similar role in transmission.
Characteristics
Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.
The clinical features of dengue fever vary according to the age of the patient. Infants and young children may have a fever with rash. Older children and adults may have either a mild fever or the classical incapacitating disease with abrupt onset and high fever, severe headache, pain behind the eyes, muscle and joint pains, and rash.
Dengue haemorrhagic fever (DHF) is a potentially deadly complication that is characterized by high fever, often with enlargement of the liver, and in severe cases circulatory failure. The illness often begins with a sudden rise in temperature accompanied by facial flush and other flu-like symptoms. The fever usually continues for two to seven days and can be as high as 41°C, possibly with convulsions and other complications
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