Dengue fever is a flu-like illness spread by the bite of an infected mosquito. Dengue haemorrhagic fever is a severe, often fatal, complication of dengue fever.
Causes: Dengue and dengue haemorrhagic fever are caused by any of the dengue family of viruses. Infection with one virus does not protect a person against infection with another.
Dengue is spread by the bite of an Aedes mosquito. The mosquito transmits the disease by biting an infected person and then biting someone else.
Occurrence: Dengue viruses occur in most tropical areas of the world. Dengue is common in Africa, Asia, the Pacific, Australia, and the Americas. It is widespread in the Caribbean basin.
Dengue is most common in cities but can be found in rural areas. It is rarely found in mountainous areas above 4,000 feet.
The mosquitoes that transmit dengue live among humans and breed in discarded tires, flower pots, old oil drums, and water storage containers close to human dwellings. Unlike the mosquitoes that cause malaria, dengue mosquitoes bite during the day.
Signs and symptoms: Dengue fever usually starts suddenly with a high fever, rash, severe headache, pain behind the eyes, and muscle and joint pain.
The severity of the joint pain has given dengue the name "breakbone fever." Nausea, vomiting, and loss of appetite are common. A rash usually appears 3 to 4 days after the start of the fever.
The illness can last up to 10 days, but complete recovery can take as long as a month. Older children and adults are usually sicker than young children.
Most dengue infections result in relatively mild illness, but some can progress to dengue haemorrhagic fever. With dengue haemorrhagic fever, the blood vessels start to leak and cause bleeding from the nose, mouth, and gums. Bruising can be a sign of bleeding inside the body. Without prompt treatment, the blood vessels can collapse, causing shock (dengue shock syndrome). Dengue haemorrhagic fever is fatal in about 5 percent of cases, mostly among children and young adults.
How soon after exposure do symptoms appear?
The time between the bite of a mosquito carrying dengue virus and the start of symptoms averages 4 to 6 days, with a range of 3 to 14 days. An infected person cannot spread the infection to other persons but can be a source of dengue virus for mosquitoes for about 6 days.
Diagnoses: Dengue is diagnosed by a blood test.
Risk factors: Anyone who is bitten by an infected mosquito can get dengue fever. Risk factors for dengue haemorrhagic fever include a person's age and immune status, as well as the type of infecting virus.
Persons who were previously infected with one or more types of dengue virus are thought to be at greater risk for developing dengue haemorrhagic fever if infected again.
Treatment: There is no specific treatment for dengue. Persons with dengue fever should rest and drink plenty of fluids. They should be kept away from mosquitoes for the protection of others. Dengue haemorrhagic fever is treated by replacing lost fluids. Some patients need transfusions to control bleeding.
HOW COMMON IS DENGUE?
In tropical countries around the world, dengue is one of the most common viral diseases spread to humans by mosquitoes. Tens of millions of cases of dengue fever and up to hundreds of thousands of cases of dengue haemorrhagic fever occur each year.
IS DENGUE AN EMERGING INFECTIOUS DISEASE?
Yes. All types of dengue virus are re-emerging world-wide and causing larger and more frequent epidemics, especially in cities in the tropics.
The emergence of dengue as a major public health problem has been most dramatic in the western hemisphere. Dengue fever has reached epidemic levels in Central America and is threatening the United States.
SEVERAL FACTORS ARE CONTRIBUTING TO THE RESURGENCE OF DENGUE FEVER:
-- No effective mosquito control efforts are underway in most countries with dengue.
-- Public health systems to detect and control epidemics are deteriorating around the world.
-- Rapid growth of cities in tropical countries has led to overcrowding, urban decay, and substandard sanitation, allowing more mosquitoes to live closer to more people.
-- The increase in non-biodegradable plastic packaging and discarded tires is creating new breeding sites for mosquitoes.
-- Increased jet air travel is helping people infected with dengue viruses to move easily from city to city.
Dengue haemorrhagic fever is also on the rise. Persons who have been infected with one or more forms of dengue virus are at greater risk for the more severe disease. With the increase in all types of virus, the occurrence of dengue haemorrhagic fever becomes more likely.
Prevention: There is no vaccine to prevent dengue. Prevention centers on avoiding mosquito bites when travelling to areas where dengue occurs. Eliminating mosquito breeding sites in the areas is another key prevention measure.
AVOID MOSQUITO BITES WHEN TRAVELING IN TROPICAL AREAS:
-- Use mosquito repellents on skin and clothing.
-- When outdoors during times that mosquitoes are biting, wear long-sleeved shirts and long pants tucked into socks.
-- Avoid heavily populated residential areas.
-- When indoors, stay in air-conditioned or screened areas. Use bednets if sleeping areas are not screened or air-conditioned.
ELIMINATE MOSQUITO BREEDING SITES IN AREAS WHERE DENGUE MIGHT OCCUR:
-- Eliminate mosquito breeding sites around homes. Discard items that can collect rain or run-off water, especially old tires.
• Regularly change the water in outdoor bird baths and pet and animal water containers.