Dengue fever

Dengue fever originated as a tropical disease that is transmitted by a mosquito. People with dengue fever experience flu-like symptoms and, depending on the symptoms, a lengthy recovery process. Travelers should inform themselves about the spread of the disease in the destination country and take measures to protect themselves.

At a glance

  • Dengue fever is an infectious disease that is found primarily in the tropics and subtropics.
  • The original dengue virus is transmitted by the Aedes mosquito.
  • Typically, the symptoms are flu-like in nature and full recovery can take a long time.
  • In serious cases, the illness can lead to bleeding and life-threatening cardiovascular failure.
  • Travelers should inform and protect themselves well.

Note: The information in this article cannot and should not replace a medical consultation and must not be used for self-diagnosis or treatment.

Dengue: mosquito sitting on a man’s hand.

What is dengue fever?

Dengue fever is a viral disease transmitted by the Aedes mosquito. It is found primarily in tropical and subtropical regions of Asia, Latin America, and Africa. Dengue fever affects both warm countries near the equator and temperate zones located approximately between the 25- and 40-degree north and south latitudes. However, it has spread north, with cases seen in Europe, for example, in Portugal, France, and Italy.

Dengue occurs mainly in tropical and sub-tropical regions of Asia, Latin America and Africa.

Three billion people in over 100 countries live in areas at risk of dengue fever. It is estimated that approximately 400 million people become infected with the virus each year.

If you have plans to travel to an area at risk of dengue fever, first learn more about the measures you should take to protect yourself (see the section about prevention).

Detailed information is available on the German Federal Foreign Office’s website. It explains the current health risks and suitable preventative measures for various countries.

You will also find a Dengue fever fact sheet.

What are the symptoms of dengue fever?

Symptoms of the disease can be mild or severe.

Mild symptoms

The viral infection typically causes flu-like symptoms. They include fever, chills, and in some cases severe bone and limb pain, as well as intense headaches. Other symptoms include nausea and vomiting. After a short fever-free phase, the fever spikes again and a skin rash which looks similar to measles can appear.

For most patients, the symptoms subside after three to seven days. However, it can take weeks until they feel completely healthy again.

After recovery, the patient is immune to the virus and cannot become infected again. It is important to note though that there are four different variants of the virus; cross-immunity cannot be attained.

An incubation period of three to 14 days can pass from the time of infection to the presence of symptoms.

Severe symptoms

Approximately two to four percent of those infected experience severe symptoms. Indigenous children living in risk areas are particularly affected. This severe form is known as dengue hemorrhagic fever (DHF). Hemorrhagic means that bleeding occurs. A decline in health begins after approximately five days and is accompanied by restlessness, anxiety, cold sweats, and heart palpitations. The blood vessels become more permeable, which leads to a blood clotting disorder.

This results in a poor supply of blood to the lungs, liver, kidney, and intestinal tract, and later the heart and brain as well. Eventually the infected person experiences cardiovascular failure. This is known as dengue shock syndrome. If left untreated in this dangerous form, the disease can lead to death. The survival rate rises with treatment in an intensive care unit.

What are the causes of dengue fever?

The dengue virus is primarily transmitted by diurnal Aedes mosquitoes. There are four different virus variants. A person who has survived an infection of one of the four virus variants is most likely immune to this variant for their entire life. Furthermore, immunity to the other variants has been reported, however only for approximately one to two years.

Important: Since there are four different virus subtypes, it is possible to become infected by dengue fever four times. There is a slightly heightened risk of becoming ill more severely from dengue fever the second time.

It is thought that the antibodies created by the body after the first instance of the disease can intensify the symptoms of a new infection by a different dengue variant.

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What are the known risk factors?

The risk to travelers of becoming sick with dengue fever depends on multiple factors.

They include:

  • the travel destination
  • the duration of the trip
  • the season
  • measures taken to repel mosquitoes
  • the current situation in the travel destination (e.g., increased number of cases)
  • a previous infection of the dengue virus

Travelers should always inform themselves of the current situation in their travel destination and take suitable protective measures (see the section on prevention).

How common is dengue fever?

According to estimates, approximately 400 million people worldwide contract the virus every year. Observations over a longer period of time indicate a sharp rise in the number of infections: dengue infections occur 15 times more often today than 20 years ago. The number of deaths quadrupled between the years 2000 and 2015. This development could be a result of an increased awareness of the disease and that more cases are being reported. Other possible causes under discussion are the increase in population density in metropolitan areas, climate change, and an increased proliferation of the mosquitoes that transmit the disease.

More than 90 percent of those infected are children. At the same time, they are at highest risk for a severe case of the disease or even death.

In Germany, 600 to 800 cases of travel-related dengue fever are reported each year. The main countries of infection for German patients are popular travel destinations in South and Southeast Asia, such as Thailand, but also Central and South America.

In the first half of 2019, 634 dengue fever cases were reported to the Robert Koch Institute. This number was significantly higher than that of the previous year. At 43 percent, Thailand was by far the most frequently reported country for infections, followed by Indonesia (11 percent), Sri Lanka and Brazil (four percent each), and Cambodia, Vietnam, Cuba, Mexico, and the Philippines (each with three percent).

How can travelers protect themselves from dengue fever?

In particular, the skin must be protected. Other measures should be taken in the accommodation where the traveler is staying.

Dengue can be prevented by various measures: mosquito nets treated with insecticide, air conditioning, bright and robust clothing, long sleeves and insect spray.

Protecting the body

The most important measure travelers can take is consistent protection of the entire body from mosquitoes. The World Health Organization recommends mosquito repellent for the skin that contains the active substances DEET (diethyltoluamide) or icaridin.

Light-colored, tight, and long-sleeved clothes are recommended. They should be coated with anti-insect spray, since Aedes mosquitoes can also pierce the material. This type of protection is very important primarily during the day, since dengue-transmitting mosquitoes are diurnal. However, these mosquitoes can be active around artificial light also in the evening or at night.

Accommodation protection measures

Mosquito netting treated with insecticide must be used in sleeping accommodations. Air conditioners can also lower the risk of being bitten.

Detailed information is available on the German Federal Foreign Office’s website. It explains the current health risks and suitable preventative measures for various countries.

Vaccine

As of October 2018, there is a vaccine that protects from all four dengue virus variants. This vaccine has been approved by the European Medicines Agency (EMA) only for people who:

  • live in an area at risk,
  • are between the ages of nine and 45, and
  • have already been infected by a lab-confirmed dengue infection.

Approval by the EMA also applies to the French overseas departments and overseas territorial bodies, such as La Réunion, Guadeloupe, Mayotte or French Polynesia. For people who live in risk areas outside of the European Union, the regulations of the respective country apply. 

Important: The vaccine is not approved for travelers.

How is dengue fever diagnosed?

A blood sample obtained as early as possible is required to determine the presence of a dengue infection. If infection is suspected, the doctor should be informed when and where the patient has traveled.

How is dengue fever treated?

There is no treatment for the virus itself. Only the symptoms are treated. Ambulant treatment is usually possible.

The most important treatment measures are:

  • drinking plenty of fluids
  • leg compresses to bring down the fever
  • for pain preferably acetaminophen (paracetamol)

Important: The active substance acetylsalicylic acid (ASS), typically used to treat pain, should not be used. It prevents clotting, which can worsen the illness.

If the following problems arise, treatment in a hospital should be sought:

  • insufficient fluid intake or diminished urination
  • a decline in overall health, restlessness, or apathy
  • a low blood platelet count (denoted as thrombocytes in a lab report)
  • bleeding

Reviewed by the German Society for Tropical Medicine, Travel Medicine and Global Health (DTG). As at:

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