WHO updates fact sheet on Dengue and Severe Dengue (6 April 2017)

The World Health Organization (WHO) has updated its fact sheet on Dengue and Severe Dengue.

Background Information:

Dengue is a mosquito-borne viral disease that is transmitted by female mosquitoes mainly of the species Aedes aegypti and, to a lesser extent, Ae. albopictus. This mosquito also transmits chikungunya, yellow fever and Zika infection.

Dengue is widespread throughout the tropics, with local variations in risk influenced by rainfall, temperature and unplanned rapid urbanization.

Severe dengue (also known as Dengue Haemorrhagic Fever) affects most Asian and Latin American countries and has become a leading cause of hospitalization and death among children and adults in these regions.

There are 4 distinct, but closely related, serotypes of the virus that cause dengue (DEN-1, DEN-2, DEN-3 and DEN-4). Recovery from infection by one provides lifelong immunity against that particular serotype. However, cross-immunity to the other serotypes after recovery is only partial and temporary. Subsequent infections by other serotypes increase the risk of developing severe dengue.

Key Messages:

One recent estimate indicates 390 million dengue infections per year, of which 96 million manifest clinically (with any severity of disease).

Another study, of the prevalence of dengue, estimates that 3.9 billion people, in 128 countries, are at risk of infection with dengue viruses.

The disease is now endemic in more than 100 countries.

Among travellers returning to Europe from low- and middle-income countries, dengue is the second most diagnosed cause of fever after malaria.

An estimated 500 000 people with severe dengue require hospitalization each year, and about 2.5% of those affected die.

The Aedes aegypti mosquito is the primary vector of dengue. The virus is transmitted to humans through the bites of infected female mosquitoes. After virus incubation for 4–10 days, an infected mosquito is capable of transmitting the virus for the rest of its life.

Aedes aegypti lives in urban habitats and breeds mostly in man-made containers. Unlike other mosquitoes Ae. aegypti is a day-time feeder; its peak biting periods are early in the morning and in the evening before dusk. Female Ae. aegypti bites multiple people during each feeding period.

Dengue should be suspected when a high fever (40°C/104°F) is accompanied by 2 of the following symptoms:

  • severe headache,
  • pain behind the eyes,
  • muscle and joint pains,
  • nausea,
  • vomiting,
  • swollen glands or
  • rash.

Symptoms usually last for 2–7 days.

Severe dengue is a potentially deadly complication due to

  • plasma leaking,
  • fluid accumulation,
  • respiratory distress,
  • severe bleeding, or
  • organ impairment.

Warning signs occur 3–7 days after the first symptoms in conjunction with a decrease in temperature (below 38°C/100°F) and include:

  • severe abdominal pain,
  • persistent vomiting,
  • rapid breathing,
  • bleeding gums,
  • fatigue,
  • restlessness and
  • blood in vomit.

The next 24–48 hours of the critical stage can be lethal; proper medical care is needed to avoid complications and risk of death.

There is no specific treatment for dengue/ severe dengue, but early detection and access to proper medical care lowers fatality rates below 1%. Maintenance of the patient’s body fluid volume is critical to severe dengue care.

In late 2015 and early 2016, the first dengue vaccine, Dengvaxia (CYD-TDV) by Sanofi Pasteur, was registered in several countries for use in individuals 9-45 years of age living in endemic areas.

At present, the main method to control or prevent the transmission of dengue virus is to combat vector mosquitoes through:

  • preventing mosquitoes from accessing egg-laying habitats by environmental management and modification;
  • disposing of solid waste properly and removing artificial man-made habitats;
  • covering, emptying and cleaning of domestic water storage containers on a weekly basis;
  • applying appropriate insecticides to water storage outdoor containers;
  • using of personal household protection such as window screens, long-sleeved clothes, insecticide treated materials, coils and vaporizers;
  • improving community participation and mobilization for sustained vector control;
  • applying insecticides as space spraying during outbreaks as one of the emergency vector-control measures;
  • active monitoring and surveillance of vectors should be carried out to determine effectiveness of control interventions.

Careful clinical detection and management of dengue patients can significantly reduce mortality rates from severe dengue.

Useful Links:

Link to the updated fact sheet:

http://www.who.int/mediacentre/factsheets/fs117/en/

Link to WHO Position Paper on Dengue Vaccine:

http://www.who.int/wer/2016/wer9130.pdf

Link to WHO’s Global Strategy for Dengue Prevention and Control 2012-2020 (English) [PDF]:

http://apps.who.int/iris/bitstream/10665/75303/1/9789241504034_eng.pdf

Link to Executive Summary of the above document (English) [PDF]:

http://www.who.int/denguecontrol/9789241504034_executive_summary.pdf?ua=1

 

 

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