What is dengue fever?
Dengue fever is a mosquito-borne viral infection, common in Southeast Asia, the Indian subcontinent, the Caribbean, Africa, the Americas, Australia and the Pacific islands.
Dengue fever is transmitted by the bite of a mosquito (typically of the species Aedes aegypti) and usually causes flu-like symptoms such as fever, pain in the muscles and general weakness.
Although most cases of dengue fever are relatively mild, even mild infections can cause painful or debilitating symptoms. In rare cases, the condition can turn into severe dengue, known as dengue hemorrhagic fever, which can cause acute health problems and be potentially life-threatening.
Dengue fever is self-limiting in the majority of cases, meaning it will be dealt with by the body’s immune system and disappear naturally. There is no specific treatment for cases of mild dengue fever besides supporting the body with rest and plenty of fluids. In severe cases, treatment will be more intensive, with a stay in hospital likely.
Symptoms of dengue fever
- Fever, above 38 C / 100.4 F
- Severe headaches
- Body aches, including muscle and joint pain
- Pain behind the eyes
- Nausea and vomiting
- A widespread red body rash
- Loss of appetite
Good to know: People with these symptoms, especially those currently in or recently returned from an area with a known danger of dengue infection, should see a medical professional as soon as possible.
The symptoms of dengue fever can often be confused with flu or another virus. This is especially the case in young adults, who tend to experience a milder form of the symptoms of the infection caused by the virus. As well as seeing a doctor, the free Ada app can be used to carry out a symptom assessment.
The critical stage of dengue fever begins when the initial fever breaks and lasts between 24 and 48 hours. It is known as the critical phase because, although most affected people improve, some people begin to show severe symptoms. This is also known as dengue hemorrhagic fever. Dengue hemorrhagic fever is most common in children who are younger than 15 years of age and people who have had the infection previously.
Symptoms of dengue hemorrhagic fever include:
- Severe belly pain
- Bleeding from any part of the body, most commonly the gums
- A very high fever
- Persistent vomiting or vomiting blood
- Rapid breathing or difficulty breathing
- A skin rash that is red and blotchy, and may result in peeling skin
- Listlessness and fatigue
If the symptoms of dengue hemorrhagic fever are not well managed, they may lead to severe bleeding and consequently shock. This may develop into dengue shock syndrome. This condition can cause death if not promptly and adequately treated. If someone with dengue fever starts to show any of the symptoms listed above, they should seek medical attention again as soon as possible, as proper management of the disease in the next hours is important if complications are to be avoided. There is no treatment other than supportive care.
Good to know: There are four main strains, or serotypes,of the virus that are known to cause dengue fever. Infection with one strain of the virus confers immunity against only that strain. It is then still possible to be infected by one of the other strains. The risk of developing the severe form of the disease increases with each subsequent infection.
Causes of dengue fever
Dengue fever is spread by mosquitoes, not from person to person. These mosquitoes are most commonly found in tropical and warm areas and become most active at night or in the early morning.
Today, dengue fever is common in many tropical areas of the world. While everyone is at equal risk of being bitten by mosquitoes and contracting the virus, those with weakened immune systems or those who have previously been infected with the virus are most at risk of dengue hemorrhagic fever.
Aedes aegypti mosquitoes
The female Aedes aegypti mosquito is the main carrier of the virus that causes dengue fever. The dengue virus is passed on via a bite from one of these mosquitoes, which generally acquire the virus from the blood of an infected individual.
Aedes aegypti mosquitoes typically breed indoors in artificial water containers and spend the majority of their lifespan in or around the location where they emerge. They are typically most active in the early morning and the early evening. However, Aedes aegypti are capable of biting and spreading the virus in any location, indoor or outdoor, at any time of the day.
Aedes aegypti are the mosquito variety most closely associated with dengue fever. However, other mosquito types have also had dengue fever outbreaks attributed to them. These mosquito types include Aedes albopictus, Aedes polynesiensis and several species of the Aedes scutellaris complex.
Diagnosing dengue fever
People with the symptoms of dengue fever should seek a medical opinion as quickly as possible. Dengue fever is diagnosed with a series of blood tests used to identify the virus itself, the immune reaction to the infection and other effects the infection may have on the body, such as reduced blood clotting.
Telling dengue fever, Zika virus, yellow fever and chikungunya virus apart
Dengue fever, chikungunya fever, yellow fever and Zika virus are all spread by the same two species of mosquito - Aedes aegypti and Aedes albopictus. The viruses that cause dengue, Zika and yellow fever are members of the family Flaviviridae; the virus that causes chikungunya fever belongs to the family Alphaviridae.
It can sometimes be difficult to tell these various mosquito-borne diseases apart from the symptoms alone, which are similar. However, all of these disorders can be diagnosed using blood tests.
The symptoms of chikungunya include:
- Severe joint pain
- Muscle pain
- Joint swelling
- A rash
The joint pain associated with chikungunya is very severe. The disease can relapse; people who have been infected with the chikungunya virus can sometimes have pain in the joints in the months following the acute phase of the illness.
The symptoms of yellow fever include:
- Nausea and vomiting, sometimes vomiting blood
- Lower back pain
More serious symptoms such as jaundice, decreased urination, redness of the eyes and face, heart arrhythmia and bleeding may also occur.
Most people with Zika virus infection do not show symptoms. If symptoms do occur, they are usually mild and may include:
- A rash
- Muscle and joint pain
Good to know: For most people, Zika is not harmful. However, it may be more serious for pregnant women, as it is known to cause birth defects.
Travellers who have recently returned from tropical or subtropical parts of the world and begin showing symptoms such as fever can do a free symptom assessment using the Ada app. However, even if their symptoms are not severe, they should also go to the doctor.
Dengue fever treatment
If dengue fever is suspected, medical attention should be sought immediately. Doctors will generally prescribe rest and plenty of fluids to help support the body in combating the infection.
There is currently no effective vaccine or specific medication to treat dengue fever. Pain relievers containing acetaminophen, also known as paracetamol, can be used to manage some of the symptoms, mainly body pain and headache. People with dengue fever should take care to consume enough fluids to remain well-hydrated. People with a fever can be cooled down using a wet towel or sponge.
Good to know: If symptoms of dengue fever persist, urgent medical attention should be sought to avoid the risk of complications.
Preventing dengue fever
As there is no specific treatment, prevention is key to combating dengue fever. If living or traveling in tropical areas, taking steps to avoid the reproduction of mosquitoes and avoid being bitten by mosquitoes is the most effective method of doing this.
Reducing the mosquito population by identifying and removing locations where they can breed should be the first step in dengue fever prevention. These locations include birdbaths, buckets, old tires and flower pots, or anywhere where standing water can collect.
Other effective ways to protect yourself against mosquitoes include:
- Insect repellents. To be used even when indoors and applied directly to the skin as well as to clothing. Parents should be aware that children may need repellent that has been specially approved for use on children.
- Loose and protective clothing. Mosquitos are able to bite through tight clothing, so garments should be loose and cover as much of the body as possible. Light colours are also preferable to dark.
- A mosquito net. When sleeping, a mosquito net is vital for everyone, especially children. If possible, the net should be treated with insecticide.
Vaccines for dengue fever
20 countries globally have licensed a dengue fever vaccine named CYD-TDV. The vaccine does not offer total protection against dengue fever, and its efficacy may differ according to age and previous exposure to the viruses that cause dengue fever.
Dengue fever and hemorrhagic fever prognosis
Generally, dengue fever is a self-limiting infection that naturally passes within two weeks of infection. People who develop dengue hemorrhagic fever have a higher risk of life-threatening complications.
Advice for travelers
People traveling to regions where dengue fever is a risk, including Southeast Asia, the Indian subcontinent, the Caribbean, Africa, the Americas, Australia and the Pacific islands should be sure to think about prevention before they arrive.
Travelers should ensure they pack:
- A supply of insect repellent
- Loose, protective clothing
- Their own mosquito net to reduce the risk of being bitten.
After arriving, efforts should be made to avoid locations where mosquitoes breed, such as stagnant water, and travelers should take special care during times of the day when mosquitoes are most active. Generally, this is at night, dusk and dawn.
Good to know: If a person begins to display any signs or symptoms of dengue fever when traveling or shortly after returning home, immediate medical advice should be sought. It is rare for travelers with dengue to develop complications or dengue hemorrhagic fever.
Countries and regions affected by dengue fever
Dengue fever is a spreading global concern. Before the 1970s, dengue fever was found in only nine countries, but the disease is now found in over one hundred countries worldwide, most of them in the tropics or subtropics.
Good to know: The risk of contracting dengue fever is not the same in all areas where the disease is found; it also varies within affected regions. Risk profiles may change depending on the mosquito population, the temperature, rainfall levels and whether the region has adequate civil infrastructure or is undergoing urban development. The chances of contracting dengue tend to be higher in developing countries than in developed countries, for example. Travelers should take precautions based on whether the region to which they are travelling has dengue present, not on whether they are very likely to encounter it. For more information on the level of risk in particular regions, consult a medical professional or a travel clinic, or check online travel advisories for the region.
In Asia and the Middle East, affected areas include:
- Sri Lanka
- Saudi Arabia
- The Philippines
- Costa Rica
- Many islands in the Caribbean
- The United States of America, predominantly the warmer southern regions
No cases have been reported in Canada.
- French Polynesia
- Indonesia, including Bali
- The Cook Islands
- The Solomon Islands
- Australia, predominantly the tropical regions
No cases have been reported in New Zealand.
In East and Central Africa, affected regions include:
- Tanzania and Zanzibar
- Democratic Republic of the Congo
In Southern Africa, regions affected include:
- The Comoros
- The Seychelles
- Mauritius and Reunion
- South Africa
In West Africa, regions affected include:
- Equatorial Guinea
- Cape Verde
- Burkina Faso
- Cote d’Ivoire
This list is not exhaustive. If you have recently travelled to an affected area and are now experiencing symptoms that worry you, you can do a free symptom assessment using the Ada app at any time.
Dengue fever in pregnancy
There is as yet limited information on the effects of dengue fever during pregnancy, although it is a very common cause of fever in pregnant women in areas in which the disease is endemic. There is some evidence that having dengue fever during pregnancy slightly increases the risk of excessive bleeding after giving birth known as postpartum hemorrhage, preterm birth and low birthweight. 
Dengue fever FAQs
Q: Is dengue fever contagious?
A: No. Dengue fever is not spread from person to person but via infected mosquitoes.
Q: Can dengue fever be fatal?
A: Yes. However, this is rare. Dengue fever with complications, and especially dengue hemorrhagic fever, can be fatal if they are not treated.
Q: Can dengue fever come back after you recover?
A: No. Dengue fever is not recurrent in the same way that, for example, malaria is. However, it is possible to have dengue fever more than once. A person who has had dengue fever caused by a particular strain of dengue virus may thereafter be immune to that strain, but may still be prone to infection by one of the other strains.
Q: What virus causes dengue fever?
A: Dengue fever is caused by four closely related viruses, known as serotypes: DEN-1, DEN-2, DEN-3 and DEN-4. DEN-5 may also be responsible for a few dengue infections. Although each of these serotypes interacts with the body in a different way, each virus causes the same symptoms to manifest. It is possible to be immune to one serotype while still being prone to infection by one or more of the other serotypes.
Q: What is the difference between dengue fever and malaria?
A: Both dengue fever and malaria are spread by mosquitoes, but the diseases themselves are not related. Dengue is spread by Aedes aegypti and Aedes albopictus mosquitoes, while malaria is spread by the Anopheles mosquito. Dengue fever is caused by the DEN virus, of which there are four or possibly five strains known to infect humans. Malaria, however, is not caused by a virus, but by single-celled parasitic organisms of the genus Plasmodium; these are neither bacteria nor viruses. Malaria is recurrent: someone who has been infected once may experience several bouts of symptoms throughout their lives without being re-infected. Dengue fever on the other hand is not recurrent. If someone who has had dengue before shows the symptoms again after they recovery, it means that they have a new infection. Both dengue and malaria can be cured.
Q: Is dengue fever connected to Zika virus?
A: Zika virus and dengue virus belong to the same family of viruses, Flaviviridae. The viruses that case yellow fever, Japanese encephalitis and West Nile fever are in the same family. These viruses are spread by Aedes aegypti and Aedes albopictus mosquitoes.
Q: Is dengue fever connected to chikungunya fever?
A: The chikungunya virus and the dengue virus themselves are not related. However, the virus that causes chikungunya fever, known as CHIKV, can be carried by some of the same species of mosquitoes that carry the dengue virus, Aedes aegypti and Aedes albopictus. The same species of mosquitoes may also carry Zika virus, and the areas where each disease is endemic do somewhat overlap .
Q: Can dengue fever be sexually transmitted?
A: Dengue fever cannot be sexually transmitted between humans. Mosquitoes, however, can transmit the virus to other mosquitoes during mating. Dengue fever cannot be spread from person to person.
Q: What does the dengue fever rash look like?
A: Typically, it begins as a mild, red, blotchy rash, giving the infected person a flushed appearance. As the virus develops, the rash can become more severe, turning bright red and developing lesions.
Q: When should I visit the doctor if I think I have dengue fever?
A: If there is any suspicion of dengue fever, you should visit a doctor immediately. A doctor will be able to evaluate your symptoms and make a proper diagnosis. If you have been diagnosed with dengue fever and the symptoms don’t go away or worsen in three days, a doctor should be seen once again to reduce the risk of complications.
As well as seeing a doctor, the free Ada app can also be used to carry out a symptom assessment.
Q: Which liquids should I drink?
A: People with dengue fever are encouraged to drink plenty of water, fruit juice or oral rehydration solutions to maintain electrolyte concentrations. There is some emerging evidence that staying well-hydrated can help to prevent hospitalization, although it is still very important that someone with dengue fever seek professional medical advice.
Q: What medicine can I take during dengue fever?
A: Acetaminophen, also known as paracetamol, can be used to manage the body pain and headaches that typically come with dengue fever. Anti-inflammatory medication such as ibuprofen and aspirin must be avoided as they may cause complications.
Q: Where is chikungunya fever found?
A: Areas currently affected by chikungunya include:
- the USA
- Central and South America
- the Caribbean
- South East Asia
- the West Pacific Islands
- Saudi Arabia
- the Indian Ocean Islands
- East Africa
- Central Africa
- West Africa
- Southeast Africa
Canada, Korea, Japan, Botswana, Namibia, Australia and New Zealand are not affected.
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