+Dengue

Virus

Dengue is caused by a virus of the Flaviviridae family and there are four distinct, but closely related, serotypes of the virus that cause dengue (DENV-1, DENV-2, DENV-3 and DENV-4).

Transmission

Vectors

Dengue fever is transmitted to humans through the bites of infected female mosquitoes. Aedes mosquitoes (especially Aedes aegypti) are the primary vectors. After virus incubation, an infected mosquito is capable of spreading the virus for the rest of its life.

These mosquitoes are found in tropical and subtropical regions around the world. They live in urban habitats and breed mostly in man-made containers (like buckets of water, potted plants etc) .

The mosquito can fly up to 400 meters looking for water-filled containers to lay their eggs but usually remains close to the human habitation.

Aedes aegypti is a daytime feeder: The peak biting periods are early in the morning and in the evening before dusk.

Aedes aegypti has evolved into an intermittent biter and prefers to bite more than one person during the feeding period.

Adult mosquitoes “usually” rest indoors in dark areas (closets, under beds, behind curtains). Here it is protected from wind, rain and most predators, which increases its life expectancy and the probability that it will live long enough to pick up a virus from one person and pass it on to the next.

The eggs hatch when in contact with water. Eggs can withstand very dry conditions and survive for months. Female mosquitoes lay dozens of eggs up to 5 times during their lifetime.

Infectivity

Patients who are already infected with the dengue virus can transmit the infection via Aedes mosquitoes after the first symptoms appear (during 4-5 days; maximum 12). As a precautionary approach, patients can adopt measures to reduce transmission by sleeping under a treated net especially during the period of illness with fever.

Symptoms

In many cases, the second time you get dengue, the symptoms are more severe.

Dengue fever usually occurs after an incubation period of 4-10 days after the bite of the infected mosquito. Dengue causes flu-like symptoms and lasts for 2-7 days.

High Fever (40°C/ 104°F) is usually accompanied by at least two of the following symptoms:

  • Headaches
  • Pain behind eyes
  • Nausea, vomiting
  • Swollen glands
  • Joint, bone or muscle pains
  • Rash

Severe dengue

  • When developing into severe dengue, the critical phase takes place around 3-7 days after the first sign of illness. Temperature will decrease; this does NOT mean the person is necessarily recovering.
  • On the other hand, special attention needs to be given to these warning signs as it could lead to severe dengue:
    • Severe abdominal pain
    • Persistent vomiting
    • Bleeding gums
    • Vomiting blood
    • Rapid breathing
    • Fatigue/ restlessness
  • Severe dengue causes abdominal pain and vomiting, breathing difficulties and a decrease in blood platelets that can lead to internal bleeding. +++(5)+++

When severe dengue is suspected, the person should be rushed to the emergency room or to the closest health care provider as it causes:

  • Plasma leaking that may lead to shock and/or fluid accumulation with/without respiratory distress;
  • Severe bleeding;
  • Severe organ impairment.

Severity stats

  • 75% of dengue infections are asymptomatic
  • 20% of dengue infections are mild-to-moderate
  • 5% of cases are severe dengue. 500,000 people with severe dengue require hospitalization each year and are at increased risk of death.

Prevention

Personal protection

  • Avoid mosquitoes - use nets
  • Use mosquito repellents (containing DEET, IR3535 or Icaridin)
  • Long-sleeved clothing and mosquito repellents (containing DEET, IR3535 or Icaridin) are the most viable options.

Vaccination

  • A dengue infection does not protect you from future infection because there are four dengue viruses.

Treatment

  • There is no specific treatment for dengue or severe dengue, but early detection and access to proper medical care lowers fatality rates to below 1%.
  • The transition to severe dengue is marked by difficulty breathing, mucosal bleeding, severe abdominal pain, and persistent vomiting.
  • Supportive care with analgesics, fluid replacement, and bed rest are usually helpful.
    • Aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroids should be avoided.
  • Management of severe dengue requires careful attention to fluid management and proactive treatment of hemorrhage.