Dengue Fever

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Definition

Dengue fever, also known as breakbone fever, is a mosquito-borne infection that causes a severe flu-like illness. There are four different viruses that can cause dengue fever, all of which spread by a certain type of mosquito. Dengue can vary from mild to severe; the more severe forms include dengue shock syndrome and dengue hemorrhagic fever (DHF). Patients who develop the more serious forms of dengue fever usually need to be hospitalized. 
There are currently no vaccines for Dengue fever. The best way to prevent the disease is to avoid being bitten by mosquitoes altogether. Although there is no certain treatment for Dengue, it can be treated as long as it is caught before developing into dengue shock syndrome or dengue hemorrhagic fever. 
A study published in Nature (April 2013 issue) showed that there are approximately 390 million people worldwide infected with the dengue virus each year, over three times as many as the World Health Organization's estimate of up to 100 million.
Dengue fever can be commonly found in urban parts of subtropical and tropical areas, such as Central and South America, parts of Africa, parts of Asia, the Caribbean and the Pacific.
Dengue is just as prevalent in urban districts of its range as in rural areas (unlike malaria). However, researchers from the Nagasaki Institute of Tropical Medicine in Japan reported in PLoS Medicine (August 2011 issue) that people living in rural areas have a higher risk of dengue virus infection than city dwellers. 

According to the World Health Organization (WHO):

  • Approximately 2.5 billion people, or two-fifths of the world's population, are now at risk from dengue.
  • The disease is now endemic in over 100 countries.
  • Dengue hemorrhagic fever is a leading cause of serious illness and death among children in some Asian countries.
  • In 2007, there were over 890,000 reported cases of dengue in the Americas, of which 26,000 cases were DHF.
  • Dengue infection rates among people who have not been previously exposed to the virus are commonly 40% to 50% during epidemics, but may sometimes reach 80% to 90%.
  • Approximately half-a-million people with DHF are hospitalized each year, of whom many are children. About 2.5% of these patients die.
  • DHF fatality reads may exceed 20% if untreated. If there is access to medical care with health care professionals trained in treating DHF, the death rate may be less than 1%.

 Aedes aegypti

The Aedes aegypti  mosquito can transmit the viruses that cause dengue fever. The

female mosquito lays eggs in containers with water and plants near the home . It

bites people and animals. This species can survive year round in tropical and

subtropical climates.

Signs and symptoms of Dengue Fever

 

A symptom is something the patient feels or reports, while a sign is something that other people, including the doctor detects. A headache may be an example of a symptom, while a rash may be an example of a sign. 
 
 As there are different severities of dengue fever, the symptoms can vary. 
 
 
Mild Dengue Fever - symptoms can appear up to seven days after the mosquito carrying the virus bites, and usually disappear after a week. This form of the disease hardly ever results in serious or fatal complications. The symptoms of mild dengue fever are:
  • Aching muscles and joints
  • Body rash that can disappear and then reappear
  • High fever
  • Intense headache
  • Pain behind the eyes
  • Vomiting and feeling nauseous
Dengue hemorrhagic fever (DHF) - symptoms during onset may be mild, but gradually worsen after a number of days. DHF can result in death if not treated in time. Mild dengue fever symptoms may occur in DHF, as well as the ones listed below:
  • Bleeding from your mouth/gums
  • Nosebleeds
  • Clammy skin
  • Considerably damaged lymph and blood vessels
  • Internal bleeding, which can result in black vomit and feces (stools)
  • Lower number of platelets in blood - these are the cells that help clot your blood
  • Sensitive stomach
  • Small blood spots under your skin
  • Weak pulse
Dengue shock syndrome - This is the worst form of dengue which can also result in death, again mild dengue fever symptoms may appear, but others likely to appear are:
  • Intense stomach pain
  • Disorientation
  • Sudden hypotension (fast drop in blood pressure)
  • Heavy bleeding
  • Regular vomiting
  • Blood vessels leaking fluid
  • Death

Causes of Dengue:

There are four Dengue viruses (DENV) that cause Dengue fever, all of which are spread by a species of mosquito known as the Aedes aegypti mosquito, and more rarely by the Aedes albopictus mosquito. Aedes aegypti originated in Africa, but nowadays is found in all the tropical areas around the world and prospers in and close to areas of human population. 
 The high risk regions for catching dengue fever are Central America, South America, the Caribbean and tropical Asia; more specifically - northern Argentina, northern Australia, the entirety of Bangladesh, Barbados, Bolivia, Brazil, Cambodia, Costa Rica, Dominican Republic, Guatemala, Guyana, Honduras, India, Indonesia, Jamaica, Laos, Malaysia, Mexico, Micronesia, Pakistan, Panama, Paraguay, Philippines, Puerto Rico, Samoa, Singapore, Sri Lanka, Suriname, Taiwan, Thailand, Trinidad, Venezuela and Vietnam, and increasingly in southern China. 
 The virus is transmitted from an infected mosquito to human. The process begins when a person who is infected with the Dengue virus is bitten by a mosquito, the virus is then passed on when someone else is then bitten by the infected mosquito. 
 If you have suffered from dengue fever previously it is still possible to contract it again, because of the number of different types of viruses that cause the fever. If you were infected again and became ill, there is a greater risk of developing a harsher form of the disease, such as dengue hemorrhagic fever (particularly in children). This is unusual because, normally, previous exposure to a virus causes the body to carry antibodies that allow the body to fight off the virus more easily the second time.
 
Complications of Dengue:
The majority of people suffering from dengue fever get better within 2 weeks. However, some individuals can suffer    fatigueand depression for months after the infection. Dengue fever can develop to harsher forms of the disease i.e. Dengue hemorrhagic fever and Dengue shock syndrome.
 

Diagnosis of Dengue fever

The signs symptoms of Dengue fever are similar to some other diseases, such as typhoid fever or malaria, which can sometimes complicate the chances of a prompt and accurate diagnosis. In order for a doctor to properly diagnose dengue fever they will:
  • Assess the symptoms - the doctor will take into account all your symptoms to properly diagnose whether you have dengue. Some tests may be ordered to determine whether it is a dengue infection, or some other.
  • Blood sample - this sample can be tested in a laboratory in a number of ways to find signs of the dengue virus. If the dengue virus is detected diagnosis is straightforward; if this fails there are other blood tests which can identify antibodies, antigens and nucleic acids, including: Assess your medical history - The doctor will need to know your travel history and medical history, especially if it involves mosquito exposure.
    • -ELISA (enzyme-linked immunosorbent assay)
    • -HI assay (hemagglutination inhibition assay)
    • -RT-PCR (reverse transcriptase-polymerase chain reaction)
 

Treatment options for dengue fever:

Because dengue is a virus there is no specific treatment or cure, however there are things the patient or the doctor can do to help, depending on the severity of the disease. 
 
 For milder forms of dengue the treatment methods are:
  • Prevent dehydration - high fever and vomiting can dehydrate the body. Make sure you drink clean (ideally bottled) water rather than tap water. Rehydration salts can also help replace fluids and minerals.
  • Painkillers - this can help lower fever and ease pain. As some NSAIDs (non-steroidal anti-inflammatory drugs), such as aspirin or ibuprofen can increase the risk of internal bleeding, patients are advised to use Tylenol (paracetamol) instead.
The following treatment options are designed for the more severe forms of dengue fever:
  • Intravenous fluid supplementation (IV drip) - in some harsher cases of dengue the patient is unable to take fluids orally (via the mouth) and will need to receive an IV drip.
  • Bloood transfusion - a blood transfusion may be recommended for patients with severe dehydration.
Hospital care - it is important that you be treated by medical professionals, this way you can be properly monitored (e.g. fluid levels, blood pressure) in case your symptoms worsen. If the patient is cared for by physicians and nurses experienced with the effects and complications of hemorrhagic fever, lives can be saved.

Prevention of dengue fever:

At present there is no dengue vaccine; one is currently in development. Even so, developing a vaccine to protect against four closely related viruses that can cause the disease will not be easy. 
 
 The best method of prevention is to avoid being bitten by mosquitoes. If you live or travel to an area where dengue exists, there a number of ways to avoid being bitten:
  • Clothing - your chances of being bitten are significantly reduced if you expose as little skin as possible. When in an area with mosquitoes, be sure to wear long trousers/pants, long sleeved shirts, and socks. For further protection, tuck your pant legs into your shoes or socks. Wear a hat.
  • Mosquito repellants - be sure to use one with at least 10% concentration of DEET, you will need a higher concentration the longer you need the protection, avoid using DEET on young children.
  • Use mosquito traps and nets - studies have shown that the risk of being bitten by mosquitoes is considerably reduced if you use a mosquito net when you go to sleep. Untreated nets are significantly less effective because the mosquito can bite the host through the net if the person is standing next to it. Also, even tiny holes in the netting are usually enough for the mosquito to find a way in. Nets that have been treated with insecticide are much more protective. Not only does the insecticide kill the mosquito and other insects, it is also a repellent - fewer mosquitoes are likely to enter the room(s).
  • Smell - Avoid wearing heavily scented soaps and perfumes.
  • Windows - use structural barriers, such as window screens or netting.
  • Camping - if you are camping, treat clothes, shoes and camping gear with permethrin. There are clothes which have been treated with permethrin.
  • Certain times of day - try to avoid being outside at dawn, dusk and early evening.
  • Stagnant water - the Aedes mosquito prefers to breed in clean, stagnant water. It is important to frequently check and remove stagnant water in your home/premises. 
    • Turn pails (buckets) and watering cans over; store them under shelter so water cannot accumulate in them.
    • Remove the water from plant pot plates. To remove mosquito eggs, clean and scrub them thoroughly. Ideally, do not use plant pot plates.
    • Loosen soil from potted plants. This will prevent puddles from developing on the surface of hard soil.
    • Make sure scupper drains are not blocked; do not place potted plants and other objects over the scupper drains.
    • Gully traps that are rarely used should be covered; replace gully traps with non-perforated ones, and install anti-mosquito valves.
    • Do not place receptacles under or on top of any air-conditioning unit.
    • Flower vases - change the water every other day. When you do so, scrub the inside of the vase thoroughly and rinse it out.
    • Leaves - make sure leaves are not blocking anything which may result in the accumulation of puddles or stagnant water.


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