Dengue fever

What is dengue fever?

Dengue fever is an infectious viral disease. It is transmitted by mosquitoes in tropical and sub-tropical climates. Dengue fever has become one of the fastest-spreading infectious diseases in the world over the past 30 years across the Americas, Asia, Africa and Australia. The number of countries experiencing dengue fever epidemics has grown from nine in the 1970s to more than 100 today. ^[1]

Most people infected with dengue fever suffer only temporary - though unpleasant - symptoms, but eventually make a full recovery. However, complications of dengue fever can have serious and potentially life-threatening outcomes.

Reported cases of dengue fever number in the millions per year, but because most cases of dengue fever do not lead to any serious symptoms, the number of actual infections is undoubtedly much higher. Estimates range between 50 and 390 million cases annually. ^{[1] [2]} Each year, about 500,000 people are hospitalized with severe dengue fever and tens of thousands die of the disease. There is currently no approved vaccine for dengue fever.

Causes

Dengue fever is caused by a virus transmitted via the bites of particular mosquitos, most commonly Aedes aegypti.

Types

There are four types of dengue fever virus: DENV1, DENV2, DENV3 and DENV4. They are closely related and cause similar symptoms. An infection with one type of dengue fever virus will give you lifelong immunity against that type. If you have been infected with one type of dengue virus in the past, a subsequent infection with a different dengue virus type increases the chance of severe disease (see 'Potential complications' below).

Signs and symptoms

Symptoms of dengue fever typically appear in a person 5-8 days after being bitten by a mosquito carrying the virus. Regular dengue fever symptoms include:

• High fever;
• Severe headache;
• Severe pain behind the eyes;
• Bone, muscle and joint pain;
• Rash;
• Nausea and vomiting, and;
• Bleeding from gums and under the skin, causing bruises to appear.

Symptoms normally last for 2-10 days. The bone, muscle and joint pain can be so severe that they have earned dengue fever the name 'bone-breaking disease' (though bones do not actually break).

Methods for diagnosis

Dengue fever is diagnosed via a blood test that detects the presence of the virus, or the antibodies to the virus, in the blood.

Types of treatment

There is no specific treatment for dengue fever. Antibiotics and existing antiviral medications have no effect on the virus.

If you are suffering from dengue fever, treatment will focus on managing your symptoms and supporting your body's immune system as it handles the infection.

Treatment measures can include:

• Rest;
• Drinking plenty of fluids;
• Medication to relieve pain and fever, and;
• People suspected of having dengue should not take aspirin or other anti-inflammatory medication such as ibuprofen.

Potential complications

Of those experiencing the symptoms of normal dengue, most will recover completely.

Of people who require hospitalization for dengue, 1-5% will develop complications of the disease, known as dengue hemorrhagic fever. ^[3] It is a serious condition that can lead to death. Dengue hemorrhagic fever is most common in people who have been infected with a different type of dengue fever virus in the past. Although most children only get mild symptoms if infected with the dengue virus they are more likely than adults to develop dengue hemorrhagic fever.

In dengue hemorrhagic fever, the circulatory system experiences damage and leakage from blood vessels. As a result, there can be severe bleeding and loss of blood volume, fluid on the lungs, low blood pressure, shock and sometimes death.

There is no specific treatment for severe dengue, but with good supportive medical treatment, the death rate can be lower than 1%, compared to about 15% without treatment. ^{[1] [4]} Supportive treatment can include management of fever with medication such as acetaminophen, fluid replacement (either orally or intravenously) and, in certain cases, blood transfusions.

Prevention

Bite prevention methods

A good way of reducing the chance of dengue fever is to avoid mosquito bites. The mosquitoes that spread dengue are most active during the day. In areas where the dengue fever virus is commonly found, you can protect yourself by taking the following measures:

• Wearing long trousers and long-sleeved, light-colored clothing;
• Applying tropical strength repellent containing DEET (diethyltoluamide or diethylmethylbenzamide) or repellents which contain picaridin, every 4 hours during daylight hours, and;
• Using screened accommodation.

Aedes aegypti mosquitoes are mostly active during the day. Therefore, bed nets and other night-time bite prevention strategies are less useful against dengue fever than for diseases such as malaria.

Mosquito control methods

An effective way of controlling Aedes aegypti mosquito numbers is to prevent their access to standing water that they can lay their eggs in. This requires governments and citizens to be aware of sources of standing water in their environment (containers, puddles, old tires, pots, etc.) and to empty or seal them.

Activities to reduce mosquito breeding:

• Weekly removal of items that encourage breeding (eg. tires, pot plant bases, palm fronds);
• Weekly flushing of permanent items (eg. dog bowls), and;
• Application of repellent surface spray to areas that may harbor mosquitoes (eg. under beds, behind furniture, within closets).

Vaccination

There is currently no effective vaccine against dengue fever. Several vaccine trials are in progress, but none are yet approved for use.

References

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