DENGUE FEVER

Dengue is a mosquito-borne viral infection

Transmission

• 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.
• Infected symptomatic or asymptomatic humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes.
• Patients who are already infected with the dengue virus can transmit the infection (for 4–5 days; maximum 12) via Aedes mosquitoes after their first symptoms appear.

The Aedes aegypti mosquito 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.

Characteristics

• Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.

• 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, after an incubation period of 4–10 days after the bite from an infected mosquito.

• 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.

Treatment

• There is no specific treatment for dengue fever.

• Maintenance of the patient’s body fluid volume is critical to severe dengue care.

Immunization

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.

Prevention and control

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