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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