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What is dengue fever? Dengue Fever is an illness caused by infection with a virus transmitted by the Aedes mosquito .
Symptoms of Dengue Fever Example of a skin rash due to dengue fever
Do you know…
Dengue Fever (DF) and Dengue Haemorrhagic Fever (DHF) are the most common mosquito-borne viral disease in the world.
It can be fatal.
Characteristics of the Aedes Mosquito
One distinct physical feature – black and white stripes on its body and legs.
Bites during the day.
Lays its eggs in clean, stagnant water.
Close-up of an Aedes mosquito
Only the female Aedes mosquito feeds on blood. This is because they need the protein found in blood to produce eggs. Male mosquitoes feed only on plant nectar.
On average, a female Aedes mosquito can lay about 300 eggs during her life span of 14 to 21 days.
Do you know…
Life cycle of the Aedes Mosquito 1-2 days Stagnant water Pupae 4-5 days Larvae Eggs 2-3 days
How Do Aedes Mosquitoes Transmit Diseases... Mosquito bites and sucks blood containing the virus from an infected person. Virus is carried in its body. And passes the virus to healthy people when it bites them.
This is what you can do to help…
Prevent Aedes from Breeding! Remove ALL sources of stagnant water. Deny the Aedes mosquito of any chance to breed.
10-Minute Mozzie Wipe-Out Exercise
Do the 10-Minute Mozzie Wipe-out everyday. Change water in vases on alternate days.
Do the 10-Minute Mozzie Wipe-out everyday. Remove water from flowerpot plates on alternate days.
Do the 10-Minute Mozzie Wipe-out everyday. Turn over all pails and water storage containers.
Do the 10-Minute Mozzie Wipe-out everyday. Cover bamboo pole holders when not in use.
Do the 10-Minute Mozzie Wipe-out everyday. Clear blockages and put Bti insecticide in roof gutters monthly.
Unwanted items Do not litter. Rubbish such as cups and bottles can collect rain water and breed mosquitoes.
Before you leave for holidays…
Cover all toilet bowls in your home.
Seal off the overflow pipe of the flushing cistern.
Cover all gully/floor traps.
Add sand granular insecticide to places that mosquitoes could potentially breed, such as flower vases and places where stagnant water could not be removed.
Before you leave for holidays…
Clear blockages and add Bti insecticide in roof gutters.
• Turn over all water storage containers.
Ask a relative or close friend to check your home regularly for stagnant water if you are going away for a long period of time.
Leave your contact with your neighbours or the neighbourhood police post/ centre so that you can be reached easily.
Before you leave for holidays…(Cont’d)
Spread the dengue prevention message to others… Let your family , friends and neighbours know about the dangers of breeding Mozzies!!
Dengue is an arthropod-borne disease caused by any one of four closely related viruses, ( Arbovirus ).
Characterized by fever, severe headache, backache joint pains nausea and vomiting, eye pain and rash
Occasionally produces shock and hemorrhage, leading to death.
Also called breakbone fever , dandy fever or dengue fever.
Globally, there are an estimated 50 to 100 million cases of dengue fever (DF) and several hundred thousand cases of dengue hemorrhagic fever (DHF) per year.
2.5 billion people are at risk world-wide
In the last 20 years, dengue transmission and the frequency of dengue epidemics has increased greatly in most tropical countries
It is a resurgent (re-emergent) disease worldwide in the tropics
Major global demographic changes (urbanization and population growth)
These demographic changes have resulted in sub-standard environmental sanitation that facilitates transmission of Ae. aegypti -borne disease; (Overcrowding in cities with poor sanitation)
Factors contribute to the emergence and re-emergence of arthropod-borne diseases
Increased travel by airplane resulting in a frequent exchange of dengue viruses and other pathogens.
Inadequate mosquito control services; the use of insecticide space sprays for adult mosquito proved ineffective approach for controlling Ae. aegypti . (Domestic habitat)
The emergence of resistance to insecticides linked to their increased misuse.
Mean Annual Number of DHF Cases Thailand, Indonesia and Vietnam, by Decade * Provisional data through 1998
Reported Cases of DHF in the Americas, 1970 - 1999 * Provisional data through 1999
Distribution of suspected and confirmed Dengue fever in KSA Year N. of suspected cases N. of confirmed cases 1994 1995 1996 1997 1998 1999 2000 2001 2002 673 136 57 62 31 26 17 07 11 289 6 2 15 00 3 0 0 4 Total 1020 319
Virus, Vector and Transmission
Four closely related single-stranded RNA Dengue viruses (DEN-1, DEN-2, DEN-3 and DEN-4)
Each serotype provides specific lifetime immunity, and short-term cross-immunity (A person can be infected as many as four times, once with each serotype)
All serotypes can cause severe and fatal disease
Transmission of Dengue Virus by Aedes aegypti Viremia Viremia Extrinsic incubation period DAYS 0 5 8 12 16 20 24 28 Human #1 Human #2 Illness Mosquito feeds / acquires virus Mosquito refeeds / transmits virus Intrinsic incubation period Illness
Replication and Transmission of Dengue Virus (Part 1) 1. Virus transmitted to human in mosquito saliva 2. Virus replicates in target organs 3. Virus infects white blood cells and lymphatic tissues 4. Virus released and circulates in blood 3 4 1 2
Replication and Transmission of Dengue Virus (Part 2) 5. Second mosquito ingests virus with blood 6. Virus replicates in mosquito midgut and other organs, infects salivary glands 7. Virus replicates in salivary glands 6 7 5
Aedes aegypti Mosquito
Dengue transmitted by infected female Aedes aegypti mosquito
Primarily, it is a daytime feeder
Highly domesticated tropical mosquito, lives around human habitation
Lays eggs and produces larvae preferentially in artificial water containers inside and around the houses for example; plastic containers, flower vases, buckets, used automobile tires,..
Dengue Clinical Syndromes
Undifferentiated fever (87% of Patients are asymptomatic or mild fever)
Classic dengue fever (DF)
Dengue hemorrhagic fever (DHF)
Dengue shock syndrome (DSS)
Clinical Characteristics of Dengue Classic Fever
Incubation period 3-14 days (commonly 4-7 days)
Muscle and joint pain
Dengue Hemorrhagic Fever (DHF)
Fever, or recent history of acute fever
Low platelet count (100,000/mm 3 or less)
Objective evidence of “leaky capillaries:”
elevated hematocrit (20% or more over baseline)
pleural or other effusions
4 Necessary Criteria:
Dengue Shock Syndrome (DSS)
4 criteria for DHF
Evidence of circulatory failure.
Risk Factors Reported for DHF
DHF risk is greatest for DEN-2 , followed by DEN-3, DEN-4 and DEN-1
Pre-existing anti-dengue antibody
maternal antibodies in infants
Age (fatal cases are among children and young adult).
Higher risk in secondary infections
Higher risk in locations with two or more serotypes circulating simultaneously at high levels (hyper-endemic transmission)
Increased Probability of DHF Hyperendemicity Increased circulation of viruses Increased probability of secondary infection Increased probability of occurrence of virulent strains Increased probability of immune enhancement Increased probability of DHF Gubler & Trent, 1994
Common Misconceptions about Dengue Hemorrhagic Fever
Dengue + bleeding = DHF
Need 4 WHO criteria & capillary permeability
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
DHF is a pediatric disease
All age groups are involved
DHF is a problem of low income families
All socioeconomic groups are affected
Treatment of Dengue Fever
Antipyretics (Acetaminophen) preparations to manage the pain and fever.
Avoid Aspirin and non-steroidal anti-inflammatory.