Dengue fever
Mosquito‑transmitted viral illness found in tropical and subtropical regions; symptoms range from fever and severe pain to rare hemorrhagic and shock syndromes; prevention centers on vector control and supportive care.
Overview
Dengue fever is an acute viral infection spread primarily by Aedes mosquitoes. It typically causes high fever, intense headache, pain behind the eyes, muscle and joint pain, rash and mild bleeding. Most infections are self-limiting, but a minority progress to severe forms—dengue hemorrhagic fever or dengue shock syndrome—which are medical emergencies requiring prompt hospital care. For pronunciation guidance see pronunciation and for general virus information see the dengue virus.
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Cause and transmission
The illness is caused by dengue viruses, members of the Flavivirus genus. Four main serotypes (DENV‑1 through DENV‑4) have long been recognized; infection with one serotype gives lasting immunity to that type but only short-term cross-protection against others. The principal vectors are Aedes mosquitoes, notably Aedes aegypti and A. albopictus. These mosquitoes bite mostly during daytime and breed in small collections of standing water, so urban and peri‑urban environments favor transmission.
Symptoms and complications
Initial symptoms usually appear several days after a bite and include sudden high fever, severe headache, eye pain, joint and muscle aches, and skin rash. Because of the intensity of joint and muscle pain, dengue has been nicknamed "break‑bone fever"; see more about the symptom nickname here and personal accounts there. Warning signs that suggest progression to severe disease include persistent vomiting, severe abdominal pain, bleeding from the gums or nose, rapid breathing, lethargy, and signs of circulatory failure.
Diagnosis and clinical care
Diagnosis relies on clinical features supported by laboratory tests: detection of viral RNA or antigen (NS1) is most useful early in infection, while antibody tests (IgM/IgG) can help later. There is no antiviral cure. Management is supportive: careful fluid replacement, monitoring for bleeding and shock, and use of acetaminophen for pain and fever while avoiding aspirin and nonsteroidal anti‑inflammatory drugs because of bleeding risk. Severe cases may require intravenous fluids, blood transfusions or intensive care; these are medical emergencies and timely treatment can be lifesaving (emergency guidance and hospital protocols).
Prevention and public health
Prevention focuses on reducing mosquito populations and limiting human‑mosquito contact: eliminating standing water, using window screens and repellents, and community vector control programs. Vaccines have been developed; availability and recommendations differ by country and individual serostatus. Current licensed vaccines and guidance are evolving—see vaccine information here—and travel health advice should be consulted before travel to endemic areas. There is no universal cure, and treatment remains supportive (clinical resources).
History and epidemiology
Dengue's global incidence has risen since the mid‑20th century due to urbanization, international travel, and the expansion of vector habitats. It is endemic to tropical and subtropical regions worldwide; global estimates run from tens to hundreds of millions of infections annually. For historical and surveillance records consult public health summaries. Continued research into vaccines, antiviral agents and integrated vector management remains a priority for reducing disease burden.
- Key prevention steps: remove standing water, use repellents, support community control programs.
- Seek medical care for warning signs or severe symptoms; early supportive care reduces complications.
Pathogen
→ Main article: Dengue virus
Dengue fever is caused by one of the four serotypes (DENV-1 to DENV-4) of dengue virus, it is a round enveloped virus with a diameter of 40 to 60 nm from the flavivirus family. The viral genome (unlike the DNA used by all living things) consists of ribonucleic acid (RNA). The genome is about 11,000 nucleotides long and is positive-stranded, so it can be read directly by ribosomes and used to form a protein (amino acid chain). The genome comprises only one open reading frame, which codes for a polyprotein (a long amino acid chain, which subsequently still has to be cut into the individual functional proteins).
During infection, viruses attach themselves to the cell surface of a host cell via specific receptors and are taken up by a forming endosomal vesicle. Normally, these vesicles serve to digest substances, but the virus uses them as a means of transport to reach the interior of the cell. Inside the endosome, the acidic pH induces fusion of the endosomal membrane and viral envelope, which allows the viral contents to enter the cytosol. Subsequently, the viral genome is replicated in the rough endoplasmic reticulum (ER) and in so-called vesicle packets, and after maturation in the Golgi apparatus, infectious viral particles are formed. These leave the cell and infect further host cells.
The four different serotypes occur either in demarcated or overlapping endemic zones. Phylogenetic analyses allow the individual serotypes to be subdivided into genotypes. DENV-1 and DENV-2 are divided into five genotypes each, DENV-3 and DENV-4 into four genotypes each. Molecular biology studies revealed that the endemic genotypes split from the forest or jungle (silvatic) genotypes in the last 2000 years. DENV-2 subsequently jumped to humans about 1000 years ago, DENV-4 600 years ago, and DENV-1 200 years ago (all figures ±50%). No silvatic strain of DENV-3 has been isolated so far, and consequently no statement can be made about a possible time when the virus split off.
Transmission
The most important vectors of dengue fever viruses are the females of the yellow fever mosquito (Aedes aegypti, also known as the Egyptian tiger mosquito or dengue mosquito, synonym Stegomyia aegypti) and the Asian tiger mosquito (Aedes albopictus, synonym Stegomyia albopicta), which is also spreading in Europe. In certain regions, other mosquito species are possible vectors of dengue fever, e.g. the Polynesian tiger mosquito (Aedes (Stegomyia) polynesiensis) in the southern Pacific or Aedes (Stegomyia) scutellaris in New Guinea. Other mosquito species have also been shown to be capable of pathogen transmission (vector competence).
As with other mosquito-borne arboviruses, dengue virus is ingested by a female mosquito that sucks the blood of an infected person. In the process, the viruses enter the mosquito's stomach and if the virus concentration is high enough, the virions can infect the gastric epithelial cells and multiply there. From there, they enter the hemocoel (the mosquito's blood system) and on to the salivary glands. The next time the mosquito sucks blood, it injects its saliva into the wound, allowing the virus to enter the bloodstream of the bitten primate. There is also evidence of vertical infection of dengue virus, that is, transmission from the female mosquito to her clutch and hence the larvae. This infection of vectors without a previous blood meal appears to play a role in maintaining a reservoir of virus between outbreaks.
There are two epidemiologically distinguishable infection cycles in which the virus is transmitted from mosquitoes to humans or other primates. The so-called urban cycle involves the yellow fever mosquito and the Asian tiger mosquito, which are well adapted to large urban centres and transmit dengue fever as well as other diseases there.
In addition to the urban cycle, a silvatic cycle (forest cycle or jungle cycle) exists both in Africa and in Asia, but very probably not in the Americas, in which the mosquitoes Aedes (Diceromyia) furcifer and Aedes (Stegomyia) luteocephala serve as vectors. In the jungle, mainly non-human primates are infected. While in Africa only DENV-2 circulates silvatically, in Asia this is most likely the case for all four serotypes. There is no evidence that the silvatic cycle has been involved in past dengue epidemics, but it is known that the pathogens of the silvatic cycle can also infect humans.
Questions and answers
Q: What is dengue fever?
A: Dengue fever is a tropical infectious disease caused by the dengue virus.
Q: How do people usually get the dengue virus?
A: People usually get the dengue virus from mosquitoes.
Q: Why is dengue fever also called break-bone fever?
A: Dengue fever is also called break-bone fever because it can cause so much pain that people feel like their bones are breaking.
Q: Can most people with dengue fever get better without any medical treatment?
A: Yes, most people with dengue fever can get better just by drinking enough water.
Q: What are dengue hemorrhagic fever and dengue shock syndrome?
A: Dengue hemorrhagic fever and dengue shock syndrome are medical emergencies that can kill a person if they do not receive medical treatment.
Q: Is there a vaccine that can keep people from getting the dengue virus?
A: No, there is no vaccine that can keep people from getting the dengue virus.
Q: Is there a treatment to cure dengue fever?
A: No, there is no treatment to cure dengue fever. Doctors can only provide "supportive care," which means they can only treat dengue's symptoms.
Related articles
Author
AlegsaOnline.com Dengue fever Leandro Alegsa
URL: https://en.alegsaonline.com/art/26564
Sources
- books.google.com : Desk Encyclopedia of Human and Medical Virology
- whqlibdoc.who.int : Dengue Guidelines for Diagnosis, Treatment, Prevention and Control