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Definition

Dengue fever is spread by mosquitos. ^[1]

Onset of illness

It causes symptoms similar to the flu, with some key differences. The characteristic sign that someone has been infected by dengue, is a rash that looks very similar to measles. ^[2]

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 technical term for this, is blanching of the skin with pressure.

Symptoms

There are some other, less specific symptoms, that dengue fever causes including a high fever, headaches, vomiting, and intense muscle and joint pains. In fact, the joint pain is so pronounced with dengue, that its alternative name is "breakbone fever". ^{[3] [4]}

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, ^[1] and it 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

However, not everyone has a simple recovery from dengue. In contrast to the majority now depicted 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. But most importantly, the person becomes more ill, rather than better, three to six days after the rash first develops. ^[5]

Dengue shock syndrome

Severe dengue is notable because in roughly 5% of cases ^[6], it can lead to dengue shock syndrome. Dengue shock causes a drop in the levels of blood platelets, which normally help stop bleeding.

Dengue shock hospital

The bleeding can be severe, and life-threatening, if it causes the blood pressure to drop, and critical body systems to fail. Dengue shock also requires immediate attention from medical professionals and hospitalization. ^{[1] [2]}

Causes

Dengue is a Flaviviridae virus, with five genetic types. ^{[7] [8]} Here is the virus drawn as a 3-dimensional model of the envelope protein. ^[9] 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 ^[10].

Spread

The Dengue virus is spread by several species of female mosquitoes, of the Aedes type. ^{[2] [1]} The fact that mosquitoes are the vector for the virus means that the disease is much more common in warmer climates, and below an elevation of 1000m (or 3000 feet). ^{[11] [12]}

Global warming

It also means that, the disease is more likely to be spread in the early morning and evening hours when mosquito's are more active. However all of this could change with global warming, shown here in a global animation of regional temperature over the years, with redder or warmer colors indicating higher temperatures. Recent 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. ^[13]

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

However, infection with one type of the virus, provides only short-term immunity to the others, ^[1] and subsequent infections, with a different type of the virus, increases the risk of severe complications. ^[1]

Repeated infections

A number of tests are available to confirm the diagnosis, including detecting antibodies to the virus, or its RNA. ^[2]

Prevention

A vaccine for dengue fever has been approved, and is commercially available in a number of countries. ^[14] However it is only recommended in those who have been previously infected. ^[15]

Remove standing water

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

Prevent mosquito bites

and using mosquito nets, especially when sleeping, to limit the risk of bites. ^[1]

Treatment

Treatment of mild or moderate dengue is supportive, and includes giving fluid either by mouth, or through an intravenous line. ^[2]

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. ^{[2] [16]}

Severe dengue treatment

Each year about half a million people require hospital admission for dengue related illnesses and blood transfusion. ^{[2] [1]}

Epidemiology

Dengue has become a global problem since the Second World War and is common in more than 110 countries mainly in Asia and South America. ^{[6] [17]}

Global burden

Each year between 50 and 528 million people are infected, and between 10,000-20,000 die from it. ^{[18] [19] [3] [20]}

History

The earliest descriptions of an outbreak date from the year 1779. ^[17] Its viral cause and spread, were understood by the early 20th century. ^[21]

Current efforts

Dengue fever is classified as a neglected tropical disease. ^[22] Apart from eliminating the mosquitos, work is ongoing for medication targeted directly at the virus. ^[23]

References

• WHO (2009). Dengue Guidelines for Diagnosis, Treatment, Prevention and Control (PDF). Geneva: World Health Organization. ISBN  978-92-4-154787-1.