A travel vaccine against dengue virus is currently not available. The probability of a dengue infection during a tropical holiday is currently less than 0.2 percent. Nevertheless, precautionary measures such as adequate protection against mosquito bites are recommended when travelling to risk areas.
Dengue fever is a flu-like viral disease transmitted by certain mosquitoes (Asian tiger mosquito and yellow fever mosquito). The name "dengue" comes from the Portuguese and means something like "vain/dandy" - this expression describes the painful gait of the affected person (English: "dandy"). With up to 390 million infections per year, dengue fever is considered the most important arthropod-borne infection in humans. The initial infection is usually harmless, but after surviving the initial infection, a second infection can be severe (dengue hemorrhagic fever) and fatal.
Dengue fever is transmitted by the dengue virus, which belongs to the flavivirus group. There are 4 serotypes (subgroups), with serotype DENV-2 being considered particularly virulent. The reproduction of the virus within the mosquitoes is essentially dependent on the outside temperature. For this reason, dengue virus circulates mainly in tropical and subtropical areas (southern USA, Latin America, Central Africa, India, Southeast Asia, Oceania, Australia), with the Asian Pacific region being particularly affected. Since 1990 dengue fever has also been found in Argentina, Mexico, Nepal and Hawaii. The natural foci of this pathogen (endemic areas) essentially correspond to the distribution areas of the mosquitoes that transmit the disease. In Europe, autochthonous (locally transmitted) cases of dengue fever were documented for the first time in Croatia and southern France in 2010. In 2013, there was an outbreak of dengue fever on the Atlantic island of Madeira, which is part of Portugal. In Austria, 30 to 120 dengue virus infections are diagnosed per year, so far without exception among travelers returning from endemic areas.
Primates are the only hosts of the virus. A distinction is made between a silvatic and an urban cycle. The former occurs strictly within monkey populations, although other mosquito species(Aedes furcifer, Aedes luteocephala, Aedes polynesiensis) may also play a role as vectors. The urban cycle represents human-to-human transmission. The only vectors are the Asian tiger mosquito and the yellow fever mosquito. Transmission of the virus to humans occurs through bites from female specimens of the Asian tiger mosquito(Aedes albopictus, synonym since 2004 Stegomyia albopicta) and the yellow fever mosquito (dengue mosquito or Egyptian tiger mosquito, Aedes aegypti, synonym since 2004 Stegomyia aegypti). The incubation period is 1 to 12 days (usually 3 to 7 days).
The so-called dengue triad is typical: fever, rash and headache, muscle pain, pain in the limbs, bones and joints. The rash usually begins on the trunk of the body and then spreads to the face and extremities. In the majority of cases, symptoms resolve within a week of the onset of the exanthema (acute rash). Often, an infection manifests itself only with mild signs of illness, comparable to those of a flu-like infection. An infection can also be asymptomatic (without any signs of illness). In about 2 to 4 % of cases, dengue haemorrhagic fever (DHF) is a very severe form of dengue fever. The mortality rate (lethality) of dengue haemorrhagic fever is 1 to 5 %. The health condition of the affected person often deteriorates dramatically within six days. Due to an increased permeability of the blood vessels, slight bleeding (petechiae, nosebleeds) but also uncontrolled, severe bleeding (internal bleeding, haematemesis) occurs and, as a further consequence, severe impairment of the organs (hepatitis, encephalitis, myocarditis, pancreatitis) and the entire circulation. Dengue hemorrhagic fever (DHF) is typical of a secondary infection with a different type of dengue virus. Persons who have been infected with dengue are therefore not immune but at high risk of a very severe course of the disease.
The treatment of dengue fever is only symptomatic and consists of treating the signs of the disease by reducing fever and hydration. A therapy specifically directed against the virus does not yet exist. The settlement and spread of the Asian tiger mosquito in Austria should be actively combated. Typical breeding sites for these mosquitoes are, for example, stagnant artificial waters, water residues in watering cans or in coasters of flower pots, old car tyres filled with rainwater or even uncovered rain barrels. The climate in Austria does not currently allow yellow fever mosquitoes to settle.
In addition to clinical assessment, diagnosis is based primarily on serological methods, such as the detection of IgG and IgM antibodies in the blood by means of enzyme immunoassay (EIA). In this context, attention must be paid to a pronounced cross-reactivity between different flaviviruses (e.g.: Zika virus, yellow fever virus, West Nile virus) and an associated large number of false positive findings (limited specificity). Therefore, positive EIA results must be confirmed by means of further laboratory tests (e.g. neutralisation test).
Direct pathogen detection is possible by reverse transcriptase-polymerase chain reaction (RT-PCR) in the first 5 days or by antigen detection in the first 9 days after symptom onset.
Nationale Referenzzentrale für Arbovirus-Infektionen beim Menschen
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