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Infectious diseases
( Updated at 11/05/2023 )
4 minutes of reading

What is Dengue Fever?

Dengue is a disease caused by a virus of the genus Flavivirus that is lodged in the human body through the bite of a mosquito of the genus Aedes.

What are the symptoms of Dengue?

Symptoms of dengue fever may include:

  • fever: most common symptom that lasts about 2 to 7 days
  • headache
  • muscle and joint pain
  • pain around or behind the eyes
  • Vomiting
  • red spots on the skin
  • Bleeding

The symptoms of Dengue usually appear between 4 to 7 days after the bite of the infected mosquito and last about 7 days. However, 1 in 4 people have no symptoms, including most children, or have a mild fever.

How is the disease diagnosed?

The diagnosis of Dengue is made by performing laboratory tests to identify the existence of the virus.

How is the virus transmitted?

The Dengue virus is transmitted through the bite of mosquitoes of the genus Aedes infected with the virus.

There are 4 serotypes of the Dengue virus and, therefore, it is possible to be infected four times in a lifetime, as immunity to each serotype is gained after infection.

Dengue is not transmitted from person to person, except from mother to child during pregnancy (although this route is uncommon)

What is the incubation period of the disease virus?

The virus has an incubation period of 3 to 7 days and can last up to 14 days.

What are the risk factors for Dengue virus infection?

The main risk factors for dengue transmission are related to the geographical areas that enhance the reproduction of the mosquito that transmits the virus. Thus, the following are places of risk of infection:

  • tropical or subtropical regions – continent regions of Africa, Americas, Eastern Mediterranean, Southeast Asia, Western Pacific
  • Urban areas with poor sanitary conditions
  • Places with ponds, ponds, or other standing water reservoirs

How can I prevent transmission?

The main way to prevent infection by the Dengue virus is individual protection against mosquito bites.

If you are in a region belonging to the risk locations, you should adopt the following behaviors:

  • Apply mosquito repellent all over the body, morning and evening according to the product instructions, to exposed areas. Use in pregnant women and children should be done with advice from a healthcare professional
  • prevent water from accumulating in pots or ponds
  • Wear loose-fitting clothing, preferably light-colored clothing that covers as much of the body as possible
  • Use mosquito nets
  • pay attention to the guidelines of local health authorities
  • before travelling, seek advice via Traveller Consultation or call SNS 24 – 808 24 24 24

I live in Portugal. Should I be concerned about the risk of infection with the Dengue virus?

Nope. In mainland Portugal, Aedes albopictus mosquitoes were detected for the first time at the end of July 2017. However, there is no evidence of transmission in the national territory.

In 2005, the same mosquito was detected, also for the first time, on the island of Madeira and in 2012 there was an outbreak of Dengue on this island, which resulted in more than 2,000 cases. Imported cases were also detected in mainland Portugal and in 10 other European countries.

What are the complications of Dengue infection?

Some people may develop more serious complications from dengue virus infection, such as:

  • severe dehydration
  • hypotension – low blood pressure
  • respiratory
  • dysfunction
  • severe bleeding with blood loss in the stool, vomiting or gums
  • persistent vomiting
  • severe abdominal pain
  • liver
  • failure
  • Severe dysfunction/organ failure

Which risk groups are most likely to contract the infection?

The following are part of the risk group for complications due to infection with this virus:

  • Chronically ill
  • Elderly
  • Pregnant women
  • people with a history of surgery or recent head trauma

What is the treatment for the infection?

There is no specific treatment for Dengue. Patients should seek medical advice, rest and drink plenty of fluids.

Is there a vaccine for this virus?

Yes. Currently, there is already a vaccine for this disease. It is indicated to be used and provide protection against Dengue disease in people aged between 6 and 45 years, who have had a previous infection with the Dengue virus, and to be used in endemic areas (where the virus occurs frequently).


Source: Directorate-General for Health (DGS)

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