Dengue Fever• A virus infection caused by the dengue virus• There are 4 kinds of dengue viruses• Mosquito transmits this viral disease
Areas infested with Aedes aegyptiAreas with Aedes aegypti and recent epidemic dengue
Global Status• New infections annually: 50 million• Deaths: 24,000 annually• People at risk: 2.5-3 billion• Hospitalized cases: 500,000/year – 90% of those affected are children• Disease burden: 465,000 Disability Adjusted Life Years (DALY)
Dengue in the Philippines• Endemic – 5% mortality rate – estimated 25,000 deaths/year• Occurrence: sporadic throughout the year and high cases usually occur during the rainy seasons – June-November
Aedes aegypti• The transmitter of the disease• “tiger mosquito”• A daybiting mosquito which lays eggs in clear and stagnant water found in flower vases, cans, rain barrels, old rubber tires• The adult mosquitoes rest in dark places of the house
How do Aedes Mosquitoes Transmit Disease? Virus is carried in its body.Mosquito bites and sucks And passes the virusblood containing the virus to healthy people from an infected person. when it bites them.
Incubation Period• The incubation period of dengue fever after the mosquito bite is usually 4 to 7 days
• Virus strain• Pre-existing anti-dengue antibody – previous infection – maternal antibodies in infants• Host genetics• Age• Higher risk in secondary infections• Higher risk in locations with two or more serotypes circulating simultaneously at high levels (hyperendemic transmission)
Increased Probability of DHF Hyperendemicity Increased circulation Increased probability of viruses of secondary infection Increased probability of Increased probability ofoccurrence of virulent strains immune enhancement Increased probability of DHF Gubler & Trent, 1994
ASYMPTOMATIC Undifferentiated Fever Without haemorrhageSYMPTOMATIC Dengue Fever With unusual haemorrhage Dengue No shock Haemorrhagic Fever DSS
Undifferentiated Fever• May be the most common manifestation of dengue• Prospective study found that 87% of students infected were either asymptomatic or only mildly symptomatic• Other prospective studies including all age- groups also demonstrate silent transmission
Clinical Manifestations of Dengue Fever• Fever• Headache• Muscle and joint pain• Nausea/vomiting• Rash• Hemorrhagic manifestations
• Blood pressure• Evidence of bleeding in skin or other sites• Hydration status• Evidence of increased vascular permeability-- pleural effusions, ascites• Tourniquet test
Tourniquet Test• Inflate blood pressure cuff to a point midway between systolic and diastolic pressure for 5 minutes• Positive test: 20 or more petechiae per 1 inch2 (6.25 cm2) Pan American Health Organization: Dengue and Dengue Hemorrhagic Fever: Guidelines for Prevention and Control. PAHO: Washington, D.C., 1994: 12.
• No hemorrhagic manifestations and patient is well-hydrated: home treatment• Hemorrhagic manifestations or hydration borderline: outpatient observation center or hospitalization• Warning signs (even without profound shock) or DSS: hospitalize
Patient Follow-up• Patients treated at home – Instruction regarding danger signs – Consider repeat clinical evaluation• Patients with bleeding manifestations – Serial hematocrits and platelets at least daily until temperature normal for 1 to 2 days
Patient Follow-up• All patients – If blood sample taken in first 5 days after onset, need convalescent sample between days 6 - 30 – All hospitalized patients need samples on admission and at discharge or death
Dengue Fever and DHF I & II• Fluids• Rest• Antipyretics (avoid aspirin and non- steroidal anti-inflammatory drugs)• Monitor blood pressure, hematocrit, platelet count, level of consciousness
DHF III & IV• All above treatment +• In case of severe bleeding, give fresh whole blood• Give platelet rich plasma transfusion• After BT, continue fluid therapy
Indications for Hospital Discharge • Absence of fever for 24 hours (without anti- fever therapy) and return of appetite • Visible improvement in clinical picture • Stable hematocrit • 3 days after recovery from shock • Platelets 50,000/mm3 • No respiratory distress from pleural effusions/ascitesPan American Health Organization: Dengue and Dengue Hemorrhagic Fever: Guidelines for Prevention and Control.PAHO: Washington, D.C., 1994: 69.
Do you know that…• Dengue fever and dengue hemorrhagic fever are the most common mosquito- borne viral disease in the world.• Only the female mosquito feeds on blood. This is because they need the protein found in blood to produce eggs. Male mosquitoes feed only on plant nectar.
Do you know that…• The mosquito is attracted by the body odors, carbon dioxide and heat emitted from the animal or humans.• The female Aedes mosquito searches for suitable places to lay their eggs.• Aedes are day-biters, most active during dawn and dusk.
DHF kills only by hemorrhage Patient dies as a result of shock Poor management turns dengue into DHF Poorly managed dengue can be more severe, but DHF is a distinct condition, which even well-treated patients may develop Positive tourniquet test = DHF Tourniquet test is a nonspecific indicator of capillary fragility
DHF is a pediatric disease All age groups are involved DHF is a problem of low income families All socioeconomic groups are affected Tourists will certainly get DHF with a second infection Tourists are at low risk to acquire DHF
• Cover water drums and water pails at all times to prevent mosquitoes from breeding.• Replace water in flower vases once a week.• Clean all water containers once a week. Scrub the sides well to remove eggs of mosquitoes sticking to the sides.
• Clean gutters of leaves and debris so that rain water will not collect as breeding places of mosquitoes.• Old tires used as roof support should be punctured or cut to avoid accumulation of water.• Collect and dispose all unusable tin cans, jars, bottles and other items that can collect and hold water.