Draft:Dengue

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Definition
Dengue fever is a tropical disease spread by mosquitos.

Onset of illness
It may cause symptoms similar to the flu. A characteristic sign that someone has been infected by dengue is a rash that looks similar to measles.

Blanching of rash
Another classic sign is that if handpressure is applied to the skin, an imprint will be seen for a couple of seconds after it's taken away. The term for this is blanching of the skin with pressure.



Symptoms
Dengue fever causes other, less specific symptoms including a high fever, headaches, vomiting, and intense muscle and joint pains. The joint pain is so pronounced that an alternative name for dengue is "breakbone fever".

Recovery
This graph illustrates time running to the right with tick marks for days, and a rising line means more severe symptoms. Recovery from dengue, as illustrated here, generally takes two to seven days, and is associated with a full body red rash that has small pale areas. This characteristic appearance is described as white islands in a sea of red.

Severe dengue
Not everyone has a simple recovery from dengue. In contrast to the majority depicted here as a dashed line, a small proportion of people will have worse symptoms, rather than getting better three to six days after they first get sick. This is called severe dengue, or sometimes dengue hemorrhagic fever.

Severe dengue symptoms
The signs of severe dengue are bleeding gums, worsening abdominal pain, uncontrollable vomiting, or liver enlargement. The person becomes more ill, rather than better, three to six days after the rash first develops.

Dengue shock syndrome
Roughly 5% of severe dengue cases lead to dengue shock syndrome. Dengue shock causes a drop in the levels of blood platelets that normally help stop bleeding.

Dengue shock hospital
When it causes the blood pressure to drop, and critical body systems to fail, bleeding can be severe and life-threatening. Dengue shock requires immediate attention from medical professionals and hospitalization.



Causes
Dengue is a Flaviviridae virus, with five genetic types. Here is the virus drawn as a 3-dimensional model of the envelope protein. Dengue is in the same family as other well known viruses carried by mosquitoes that cause tropical diseases, such as yellow fever, West Nile, and Zika virus.

Spread
The Dengue virus is spread by several species of female mosquitoes, of the Aedes type. Because mosquitoes are the vector for the virus, the disease is more common in warmer climates, and below an elevation of 1000 meters (or 3000 feet).

Global warming
The disease is more likely to be spread in the early morning and evening hours when mosquitos are more active. Global warming could impact how the virus is spread, as shown in this animation of regional temperature over the years, with redder or warmer colors indicating higher temperatures. Research indicates that there could be a large jump in the number of dengue cases as mosquito populations expand to more northern climates as they get warmer.

Immunity
Since Dengue fever can be caused by five different variations of the virus, immunity is complex. Infection with one type usually gives lifelong immunity to that type.

No immunity
Infection with one type of the virus provides only short-term immunity to the others, and subsequent infections with a different type of the virus increase the risk of severe complications.

Repeated infections
A number of tests are available to confirm the diagnosis, including those that detect antibodies to the virus or its RNA.

Prevention
A vaccine for dengue fever has been approved and is commercially available in a number of countries, but it is only recommended in individuals who have been previously infected or populations with a high rate of infection by the age of 9.

Remove standing water
Other methods of prevention include either removing or covering standing water to reduce the mosquito habitat.

Prevent mosquito bites
Using mosquito nets—especially when sleeping—helps limit the risk of bites.

Treatment
Treatment of mild or moderate dengue is supportive, and includes giving fluid either by mouth, or through an intravenous line.

Management of fever
For fever reduction and pain relief, paracetamol (or acetaminophen) is recommended instead of nonsteroidal anti-inflammatory drugs (like ibuprofen and aspirin), to minimize the risk of bleeding.

Severe dengue treatment
Each year about half a million people require hospital admission for dengue—related illnesses and blood transfusion.

Epidemiology
Dengue became a global problem after the Second World War and is common in more than 110 countries mainly in Asia and South America.

Global burden
Each year about 390 million people are infected, and forty thousand die from it.



History
The earliest descriptions of an outbreak was in 1779. Its viral cause and spread were understood by the early 20th century.

Current efforts
Dengue fever is classified as a neglected tropical disease. Apart from efforts to eliminate mosquitos, work is ongoing for medication targeted directly at the virus.