Dengue fever is a viral infection transmitted by mosquitoes. The infection is often mild, but can sometimes be life-threatening. Long-distance travelers are also increasingly affected. How dengue fever manifests itself, how it can be treated and how it can be prevented.
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Brief overview: Dengue fever
Definition: Viral infectious disease transmitted by mosquitoes. It occurs primarily in tropical areas, but due to increasing travel activities, cases also occur in Europe.
Vaccination: There are now vaccines against all four causative viruses.
Symptoms: Flu-like symptoms such as high fever, muscle and body aches, nausea and swollen lymph nodes.
Diagnosis: If you have symptoms after a long-distance trip, seek medical help as soon as possible. Pathogen detection is only possible in the early phase of the disease.
Therapy: There is no causal treatment. The focus is on alleviating the symptoms.
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What is dengue fever?
Dengue fever (also dengue fever) is an infectious disease that occurs primarily in the tropics and subtropics. The virus is transmitted by various mosquitoes, including Aedes aegypti (yellow fever mosquito or Egyptian tiger mosquito), and occasionally Aedes albopictus (Asian tiger mosquito).
In Germany, before the 2019 corona pandemic, a total of 1,176 cases of dengue fever occurred after long-distance travel. With increasing travel activity among the population, experts assume that the numbers will increase in the future. The main infected countries are countries in South and Southeast Asia and South and Central America. In 2019 there were particularly many cases in the Philippines, Vietnam, Malaysia and Bangladesh, as well as in Thailand and Nicaragua.
Vaccination against dengue fever
An approved vaccine against all four serotypes of the virus has been available in Europe since October 2018. However, the vaccine is only approved for people between the ages of nine and 45 who live in an endemic area and have previously had an infection. It is therefore not possible to vaccinate due to a trip to a risk area.
Another quadrivalent live vaccine was approved by the European Commission in December 2022. It has been available since March 2023 and can be vaccinated from the age of four.
Further vaccines are in development and are being tested in registration studies.
Dengue Fever: Symptoms of Infection
The time from infection, i.e. the bite of the mosquito, to the first symptoms (incubation period) is usually four to five days, but can also last up to twelve days. However, only about 25 percent of those infected develop symptoms, while the rest of the people have no symptoms.
There are two forms:
- classic dengue fever
- Dengue hemorrhagic fever (DHF) with risk of dengue shock syndrome (DSS)
Symptoms of classic dengue fever:
- flu-like symptoms
- suddenly high fever up to 40 degrees
- severe muscle, joint and limb pain
- severe headache, especially behind the eyes
- nausea and vomiting
- swollen lymph nodes
- pale skin rash (similar to measles)
The acute symptoms usually subside after about five to seven days. It can take weeks for the disease to heal. During this time, patients often feel weak and tired.
Dengue Hemorrhagic Fever (DHF)
A small proportion of those affected develop the severe form of dengue hemorrhagic fever (DHF). This complication often affects people who have had dengue fever before, but caused by a different virus.
It occurs three to seven days after the first symptoms appear
In particularly severe cases, dengue shock syndrome (DSS) can occur. As a result, people in regions with poor medical care often die.
Dengue fever is caused by virus
Dengue fever is caused by four different serotypes of a virus. They are related to the pathogens causing West Nile fever, TBE and yellow fever. The females of Aedes aegypti and Aedes albopictus can transmit dengue virus. Unlike anopheles mosquitoes, which transmit malaria and are nocturnal, dengue mosquitoes are also active during the day. When biting, the pathogens enter the blood system via the saliva of the mosquito.
Secondary infection with dengue viruses dangerous
Most initial infections with dengue viruses are silent, i.e. without or only with mild symptoms. Then the immune system has formed antibodies against the dengue virus. In the future, those affected will be immune to the serotype that triggered the disease. If the body is subsequently infected again with other dengue viruses, the second infection is more severe.
The antibodies formed during the initial infection attach themselves to the surface of the dengue virus, but cannot defeat it. This siege or masking renders the virus unrecognizable to the immune system as an enemy. This allows the pathogens to multiply unhindered. This large viral load then leads to the pronounced symptoms and often severe course of the disease.
Difficult to diagnose dengue fever
If you return from a long-distance trip and feel ill, it is best to contact a travel medicine practice or clinic. The doctor gets indications of dengue fever based on the recent trip, the symptoms and the results of a blood count.
Blood tests show whether dengue fever is actually present, or another similar tropical disease. The results are often not clear, since the pathogen can only be detected in the early phase of the disease. A differential diagnosis is important to rule out other similar tropical diseases such as malaria or yellow fever.
Treatment of dengue fever
There is no causal treatment for dengue fever. The therapy of dengue fever is therefore purely symptomatic:
- bed rest
- reduce fever
- reduce pain
- Fluid and electrolyte balance
Painkillers and antipyretics such as acetylsalicylic acid and ibuprofen are not suitable for dengue fever. These drugs thin the blood. In the case of dengue fever, the platelet count is already very low and the tendency to bleed is therefore high. Other substances, such as paracetamol, are therefore more useful.
A hospital stay is necessary if not enough liquid is consumed, the general condition deteriorates significantly or the platelet count is very low or bleeding occurs.
Intravenous fluid administration in DHF
If the disease progresses severely, a stay in the hospital is absolutely necessary. Depending on the severity of the symptoms, intensive care treatment may be necessary. The most important thing is the fluid balance, which is done intravenously.
Mild forms of dengue fever are often over after a week. The severe course often necessitates a week-long hospital stay. It often takes months for patients to fully recover from dengue fever. However, consequential damage is generally not to be expected.
Prevent dengue fever
Intensive protection against mosquito bites reduces the risk for travelers the most – especially during the day and in risk areas. This includes:
Wearing long-sleeved clothing and long pants
Use of repellents, i.e. insect-repellent skin lotions and sprays. Repellents specially developed for the tropics (e.g. with diethyltoluamide – DEET – or Icaridin) should be used, also for spraying on clothing.
Using insecticides that come in the form of a diffuser, vaporizer, or spray. The active ingredients make rooms mosquito-free, so to speak.
Sleep under a mosquito net
Safety when travelling: the risk of infection lurks here.
