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Common Viral Haemorrhagic Fevers include:Common Viral Haemorrhagic Fevers include:
Rift valley fever, Dengue fever, Rift valley fever, Dengue fever, Lassa fever,.Lassa fever,.
Ebola and marburg viral disease.Ebola and marburg viral disease.
Bovilian and argentinian haemorrhagic fever.Bovilian and argentinian haemorrhagic fever.
Haemorrhagic fever with renal syndromes.Haemorrhagic fever with renal syndromes.
Dengue is an Dengue is an arthropod-bornearthropod-borne disease caused by disease caused by
any one of four closely related viruses, (any one of four closely related viruses, (ArbovirusArbovirus).).
Characterized by fever severe headache backache Characterized by fever severe headache backache
joint pains nausea and vomiting, eye pain and rash joint pains nausea and vomiting, eye pain and rash
Occasionally produces shock and hemorrhage, Occasionally produces shock and hemorrhage,
leading to death.leading to death.
Dengue feverDengue fever
EpidemiologyEpidemiology
Globally, there are an estimated 50 to 100 million cases of Globally, there are an estimated 50 to 100 million cases of
dengue fever (DF) and several hundred thousand cases of dengue fever (DF) and several hundred thousand cases of
dengue hemorrhagic fever (DHF) dengue hemorrhagic fever (DHF) per yearper year
Average case fatality rate of DHF is about 5% Average case fatality rate of DHF is about 5%
2.5 billion people are 2.5 billion people are at riskat risk world-wide world-wide
In the last 20 years, dengue transmission and the frequency In the last 20 years, dengue transmission and the frequency
of dengue epidemics has increased greatly in most tropical of dengue epidemics has increased greatly in most tropical
countriescountries
It is a resurgent disease worldwide in the tropics It is a resurgent disease worldwide in the tropics
Major global demographic changes (urbanization and Major global demographic changes (urbanization and
population growth)population growth)
These demographic changes have resulted in sub-standard These demographic changes have resulted in sub-standard
environmental sanitation that facilitates transmission of environmental sanitation that facilitates transmission of Ae. Ae.
aegyptiaegypti-borne disease; (Overcrowding in cities with poor -borne disease; (Overcrowding in cities with poor
sanitation)sanitation)
Factors contribute to the emergence and re-Factors contribute to the emergence and re-emergence of arthropod-borne diseasesemergence of arthropod-borne diseases
Increased travel by airplane resulting in a frequent exchange Increased travel by airplane resulting in a frequent exchange
of dengue viruses and other pathogens. of dengue viruses and other pathogens.
Inadequate mosquito control services; the use of insecticide Inadequate mosquito control services; the use of insecticide
space sprays for adult mosquito proved ineffective approach space sprays for adult mosquito proved ineffective approach
for controlling for controlling Ae. aegyptiAe. aegypti. (Domestic habitat) . (Domestic habitat)
The emergence of resistance to insecticides linked to their The emergence of resistance to insecticides linked to their
increased misuse.increased misuse.
Mean Annual Number of DHF CasesMean Annual Number of DHF CasesThailand, Indonesia and Vietnam, by DecadeThailand, Indonesia and Vietnam, by Decade
* Provisional data through 1998
020406080
100120140160180200
Rep
orte
d C
ases
(T
hou
san
ds)
1950s 1960s 1970s 1980s 1990s*
Reported Cases of DHF Reported Cases of DHF in the Americas, 1970 - 1999in the Americas, 1970 - 1999
* Provisional data through 1999
0
10
20
30
40
50
60
Rep
ort
ed C
ases
(Th
ou
san
ds)
1970s 1980s 1990s*
Distribution of suspected and Distribution of suspected and confirmed Dengue fever in KSAconfirmed Dengue fever in KSA
YearYear N. of suspected casesN. of suspected cases N. of confirmed casesN. of confirmed cases
199419941995199519961996199719971998199819991999200020002001200120022002
6736731361365757626231312626171707071111
2892896622
1515000033000044
TotalTotal 10201020 319319
Dengue VirusesDengue Viruses
Four closely related single-stranded RNA Dengue Four closely related single-stranded RNA Dengue
viruses (DEN-1, DEN-2, DEN-3 and DEN-4)viruses (DEN-1, DEN-2, DEN-3 and DEN-4)
Each serotype provides specific lifetime immunity, and Each serotype provides specific lifetime immunity, and
short-term cross-immunity (A person can be infected short-term cross-immunity (A person can be infected
as many as four times, once with each serotype)as many as four times, once with each serotype)
All serotypes can cause severe and fatal diseaseAll serotypes can cause severe and fatal disease
Transmission of Dengue VirusTransmission of Dengue Virusby Aedes aegyptiby Aedes aegypti
Viremia Viremia
Extrinsic incubation
period
DAYS0 5 8 12 16 20 24 28
Human #1 Human #2
Illness
Mosquito feeds /acquires virus
Mosquito refeeds /transmits virus
Intrinsicincubation
period
Illness
Replication and TransmissionReplication and Transmissionof Dengue Virus (Part 1)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 TransmissionReplication and Transmissionof Dengue Virus (Part 2)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 MosquitoAedes aegypti Mosquito
Aedes aegyptiAedes aegypti
Dengue transmitted by infected female Dengue transmitted by infected female Aedes aegyptiAedes aegypti
mosquito mosquito
Primarily, it is a daytime feeder Primarily, it is a daytime feeder
Highly domesticated tropical mosquito, lives around human Highly domesticated tropical mosquito, lives around human
habitation habitation
Lays eggs and produces larvae preferentially in artificial Lays eggs and produces larvae preferentially in artificial
wwater containers inside and around the houses for example; ater containers inside and around the houses for example;
plastic containers, plastic containers, flower vases,flower vases, buckets, used automobile buckets, used automobile
tires,..tires,..
Clinical CharacteristicsClinical Characteristicsof Dengue Feverof Dengue Fever
Incubation period 3-14Incubation period 3-14 days (commonly 4-7 days) days (commonly 4-7 days)
FeverFever
HeadacheHeadache
Muscle and joint painMuscle and joint pain
Nausea/vomitingNausea/vomiting
RashRash
Hemorrhagic manifestationsHemorrhagic manifestations
Risk Factors Reported for DHFRisk Factors Reported for DHF
Virus serotypeVirus serotype
• DHF risk is greatest for DEN-2, followed by DEN-3, DEN-4 and DHF risk is greatest for DEN-2, followed by DEN-3, DEN-4 and DEN-1DEN-1
Pre-existing anti-dengue antibodyPre-existing anti-dengue antibody
• previous infectionprevious infection
• maternal antibodies in infantsmaternal antibodies in infants Host geneticsHost genetics AgeAge (fatal cases are among children and young adult). (fatal cases are among children and young adult). Higher risk in secondary infectionsHigher risk in secondary infections Higher risk in locations with two or more serotypes circulating Higher risk in locations with two or more serotypes circulating
simultaneously at high levels (hyperendemic transmission)simultaneously at high levels (hyperendemic transmission)
Increased Probability of DHFIncreased Probability of DHF
Hyperendemicity
Increased circulationof viruses
Increased probabilityof secondary infection
Increased probability ofoccurrence of virulent strains
Increased probability ofimmune enhancement
Increased probability of DHFGubler & Trent, 1994
Common Misconceptions aboutCommon Misconceptions aboutDengue Hemorrhagic FeverDengue Hemorrhagic Fever
Dengue + bleeding = DHFDengue + bleeding = DHF
Need 4 WHO criteria, capillary permeabilityNeed 4 WHO criteria, capillary permeability
DHF kills only by hemorrhageDHF kills only by hemorrhage
Patient dies as a result of shockPatient dies as a result of shock
Poor management turns dengue into DHFPoor management turns dengue into DHF
Poorly managed dengue can be more severe, Poorly managed dengue can be more severe, butbut DHF is a distinct DHF is a distinct
condition, which even well-treated patients may developcondition, which even well-treated patients may develop
DHF is a pediatric diseaseDHF is a pediatric disease
All age groups are involvedAll age groups are involved
DHF is a problem of low income familiesDHF is a problem of low income families
All socioeconomic groups are affectedAll socioeconomic groups are affected
Treatment Treatment
AcetaminophenAcetaminophen preparations to manage the pain and fever. preparations to manage the pain and fever.
AvoidAvoid AspirinAspirin and non-steroidal anti-inflammatory (may aggravate and non-steroidal anti-inflammatory (may aggravate
the bleeding tendency or cause Reyes syndrome in children). the bleeding tendency or cause Reyes syndrome in children).
Rest and drink plenty of Rest and drink plenty of fluidsfluids
Keep patient in screened sickroom or under a Keep patient in screened sickroom or under a mosquitomosquito netnet
Mosquito barriers are only needed Mosquito barriers are only needed until feveruntil fever subsides, to prevent subsides, to prevent
Aedes aegyptiAedes aegypti mosquitoes from biting patients and acquiring virus. mosquitoes from biting patients and acquiring virus.
PreventionPrevention
The best preventive measure is The best preventive measure is vector controlvector control
Personal protectionPersonal protection against mosquito biting against mosquito biting
• Screening doors and windowsScreening doors and windows
• Protective clothingProtective clothing
• Application of mosquito repellents on exposed skinApplication of mosquito repellents on exposed skin
Vector Control Methods:Vector Control Methods:
Biological controlBiological control
• Largely experimentalLargely experimental
• Option: place fish in containers to eat larvaeOption: place fish in containers to eat larvae
Environmental controlEnvironmental control
• Elimination of larval habitats; Cover water holding containers, Elimination of larval habitats; Cover water holding containers,
Discard artificial containers,…Discard artificial containers,…
• It is the most likely method to be effective in the long term.It is the most likely method to be effective in the long term.
Vector Control Methods:Vector Control Methods:
Chemical Control Chemical Control
Larvicides may be used to kill immature aquatic stagesLarvicides may be used to kill immature aquatic stages
Ultra-low volume fumigation is Ultra-low volume fumigation is ineffective ineffective against adult against adult
mosquitoes as mosquitoes as Aedes aegypti Aedes aegypti is fully domesticatedis fully domesticated
Mosquitoes may have resistance to commercial aerosol Mosquitoes may have resistance to commercial aerosol
sprayssprays
Dengue Vaccine?Dengue Vaccine?
No licensed vaccine at presentNo licensed vaccine at present
Effective vaccine must be tetravalentEffective vaccine must be tetravalent
Field testing of an attenuated tetravalent vaccine Field testing of an attenuated tetravalent vaccine
currently underwaycurrently underway
Effective, safe and affordable vaccine will not be Effective, safe and affordable vaccine will not be
available in the immediate futureavailable in the immediate future
Community ParticipationCommunity Participation
Prevention and mosquito control through active community Prevention and mosquito control through active community
involvement and participation to reduce larval breeding involvement and participation to reduce larval breeding
sources is the key. sources is the key.
Educate the public in the basics of dengue, such as:Educate the public in the basics of dengue, such as:
• Where the mosquito lays the eggsWhere the mosquito lays the eggs
• The link between larvae and adult mosquitoesThe link between larvae and adult mosquitoes
• General information about dengue transmission, General information about dengue transmission,
symptoms and treatmentsymptoms and treatment
Patient EducationPatient Education
Dengue fever is Dengue fever is NOTNOT contagious through person-to- contagious through person-to-person contact person contact
early early hospitalization hospitalization ReduceReduce A aegyptiA aegypti vector populations vector populations Reduce exposureReduce exposure to to A aegyptiA aegypti..
• Use insect repellent.Use insect repellent.• Sleep under a mosquito net in affected areas.Sleep under a mosquito net in affected areas.• Wear protective clothing.Wear protective clothing.
Vaccines Vaccines NOTNOT available available
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