Dengue fever is an infectious disease carried by mosquitoes and caused by any of four related dengue viruses. This disease used to be called break-bone fever because it sometimes causes severe joint and muscle pain that feels like bones are breaking, hence the name. Health experts have known about dengue fever for more than 200 years. Dengue fever is found mostly during and shortly after the rainy season in tropical and subtropical areas of Africa, Southeast Asia and China, India, Middle East, Caribbean and Central and South America, Australia and the South and Central Pacific.
The World Health Organization estimates 50 to 100 million cases of dengue infection occur each year. This includes 100 to 200 cases reported annually to the Centres for Disease Control and Prevention (CDC), mostly in people who have recently travelled abroad. Many more cases likely go unreported because some doctors do not recognize the disease. During the last part of the 20th century, cases of dengue began increasing in many tropical regions of the world. Epidemics also began occurring more frequently and with more severity. In addition to typical dengue, dengue hemorrhagic fever and dengue shock syndrome also have increased in many parts of the world.
Dengue fever is a benign acute febrile syndrome occurring in tropical regions. In some cases the virus causes increased vascular permeability that leads to a bleeding diathesis or disseminated intravascular coagulation (DIC) known as dengue hemorrhagic fever (DHF). Secondary infection by a different dengue virus serotype has been confirmed as an important risk factor for the development of DHF. In 20-30% of DHF cases, the patient develops shock, known as the dengue shock syndrome (DSS). Worldwide, children younger than 15 years comprise 90% of DHF subjects. Dengue is a homonym for the African word, ki denga pepo, which appeared in English literature during an 1827-28 Caribbean outbreak. The first definite clinical report of dengue is attributed to Benjamin Rush in 1789, but the viral aetiology and its mode of transmission via mosquitoes were not established until the early 20th century.
Dengue fever can be caused by any one of four types of dengue virus: DEN-1,DEN-2, DEN-3, and DEN-4. A person can be infected by at least two, if not all four types at different times during a life span, but only once by the same type.
Mosquitoes become infected when they bite infected humans, and later transmit infection to other people they bite. The two main species of mosquito, Aedes aegypti and Aedes albopictus, have been responsible for all cases of dengue transmitted in this country. Dengue is not contagious from person to person.
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 “break bone 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.
Most dengue infections result in relatively mild illness, but some can progress to dengue hemorrhagic fever. With dengue hemorrhagic 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 which is called dengue shock syndrome. Dengue hemorrhagic fever is fatal in about 5 percent of cases, mostly among children.
Symptoms of typical uncomplicated classic dengue usually start with fever within 5 to 6 days after you have been bitten by an infected mosquito and include
- High fever, up to 105 degrees Fahrenheit.
- Severe headache.
- Retro-orbital (behind the eye) pain.
- Severe joint and muscle pain.
- Nausea and vomiting.
The rash may appear over most of your body 3 to 4 days after the fever begins. A second rash may appear later in the disease.
Symptoms of dengue hemorrhagic fever include all of the symptoms of classic dengue plus the following additional symptoms:
- Marked damage to blood and lymph vessels.
- Bleeding from the nose, gums, or under the skin, causing purplish bruises.
This form of dengue disease causes some deaths.
Symptoms of dengue shock syndrome—the most severe form of dengue disease—include all of the symptoms of classic dengue and dengue hemorrhagic fever, plus the following:
- Fluids leaking outside of blood vessels.
- Massive bleeding.
This form of the disease usually occurs in children (but sometimes adults too) experiencing their second dengue infection. The fatality rate is 5 to 15 percent.
The health care provider can diagnose dengue fever by doing two blood tests, 2 to 3 weeks apart. The tests can show whether a sample of your blood contains antibodies to the virus. In epidemics, a health care provider often can diagnose dengue by typical signs and symptoms.
There is no specific treatment for classic dengue fever, and like most people you will recover completely within 2 weeks. To help with recovery, health care experts recommend the following:
- Getting plenty of bed rest.
- Drinking lots of fluids such as fruit juices, soups and water with electrolytes.
- Taking medicine to reduce fever.
It is advised that people with dengue fever do not to take aspirin as it dilutes blood which may complicate haemorrhage but Acetaminophen or other over-the-counter pain-reducing medicines are safe for most people. For severe dengue symptoms, including shock and coma, early emergency treatment with fluids and electrolytes can be lifesaving.
The best way to prevent dengue fever is to take special precautions to avoid contact with mosquitoes. Several dengue vaccines are being developed but none is likely to be available in the next few years. When outdoors in an area where dengue fever has been found use a mosquito repellent and dress in protective clothing such as long-sleeved shirts, long pants, socks, and shoes. Because Aedes mosquitoes usually bite during the day, be sure to use precautions especially during early morning hours before day break and in the late afternoon before dark.
Other precautions include:
- Keeping unscreened windows and doors closed.
- Keeping window and door screens repaired.
- Getting rid of areas where mosquitoes breed, such as standing water in flower pots, containers, birdbaths, discarded tires, etc.