Dengue

1. Update on Outbreak PathogenesisUpdate on Outbreak Pathogenesis
Diagnosis and other aspects of ViralDiagnosis and other aspects of Viral
Haemorrhagic Fever in Pakistan 8Haemorrhagic Fever in Pakistan 8thth
November 2006November 2006
Dr. Abbas HayatDr. Abbas Hayat
Head Department of PathologyHead Department of Pathology
Rawalpindi Medical College.Rawalpindi Medical College.

2. Aedes aegyptiAedes aegypti MosquitoMosquito

10. Historical BackgroundHistorical Background
The earliest reports of a dengue-likeThe earliest reports of a dengue-like
disease are from Chin Dynasty Chinadisease are from Chin Dynasty China
(265-420 AD). The first rigorously(265-420 AD). The first rigorously
documented outbreaks occurred almostdocumented outbreaks occurred almost
simultaneously in:simultaneously in:
Cairo and Alexandria (Egypt, 1799);Cairo and Alexandria (Egypt, 1799);
Jakarta (the called Batavia, Indonesia,Jakarta (the called Batavia, Indonesia,
1799);1799);
Philadelphia (United States, 1780);Philadelphia (United States, 1780);
Madras (India, 1780).Madras (India, 1780).

11. The virus identified in 1940's : it becameThe virus identified in 1940's : it became
a concern to armies fighting in Pacific anda concern to armies fighting in Pacific and
Asia as it was causing a large number ofAsia as it was causing a large number of
non-combat casualties to Allied andnon-combat casualties to Allied and
Japanese forces.Japanese forces.
Japanese scientists first identified theJapanese scientists first identified the
virus in 1943 and were quickly followed byvirus in 1943 and were quickly followed by
U.S. researchers. By 1956 the fourU.S. researchers. By 1956 the four
serotypes of the virus identified and everyserotypes of the virus identified and every
outbreak of the disease since has beenoutbreak of the disease since has been
due to a virus belonging to one of the fourdue to a virus belonging to one of the four
serotypes.serotypes.

13. Case fatality Rate of DF/DHF in SE AsiaCase fatality Rate of DF/DHF in SE Asia
Karachi 2005

14. BackgroundBackground
Sporadic cases of VHF in late SeptSporadic cases of VHF in late Sept
and early Octand early Oct
Media report of VHF in early Nov 2005Media report of VHF in early Nov 2005
– 2 HCWs died2 HCWs died
– Laboratory results negative for CCHFLaboratory results negative for CCHF
AKU reports increased number ofAKU reports increased number of
VHFVHF
– Clinical presentation and laboratoryClinical presentation and laboratory
results consistent with Dengueresults consistent with Dengue
Hemorrhagic feverHemorrhagic fever

15. YearYear LocationLocation No ofNo of
cases/Deathscases/Deaths
Positive by LabPositive by Lab
20032003 HaripurHaripur 1000 (7 deaths)1000 (7 deaths) 7 out of 117 out of 11
(Den Type-2)(Den Type-2)
20032003 KhushabKhushab
(Nowshera)(Nowshera)
2500 (112500 (11
deaths)deaths)
7 out of 177 out of 17
(Den Type-2)(Den Type-2)
19951995 Hubb,Hubb,
(Balochistan)(Balochistan)
-------- 57 out 7657 out 76
Den antibodiesDen antibodies
JuneJune
1994 to1994 to
Sept 95Sept 95
KarachiKarachi 145 (01 death)145 (01 death) MultipleMultiple
serotypes ofserotypes of
DengueDengue
Reported Dengue Epidemics in
Pakistan

16. Preliminary FindingsPreliminary Findings
of Karachi Outbreakof Karachi Outbreak (29(29thth
Sept – 2Sept – 2ndnd
DecDec
2005)2005)
 106 VHF patients admitted to three106 VHF patients admitted to three
tertiary care hospitalstertiary care hospitals
>34% cases confirmed by>34% cases confirmed by
serologyserology
 Mean age 29 yrs (Range 3-78yrs)Mean age 29 yrs (Range 3-78yrs)

17. 2%
28%
26%
23%
21%
< 10 y 10 to 19 20-29 30-39 > 39
Age Distribution of Patients with DHFAge Distribution of Patients with DHF
Review of Records at AKU, CHK, JPMC

18. 25%
75%
Female Male
Gender Distribution of Patients with DHFGender Distribution of Patients with DHF
Review of Records at AKU, CHK, JPMC

19. Outcome of Patients with DHF (Outcome of Patients with DHF (nn=106)=106)
Review of Records at AKU, CHK, JPMC
8%
41%
30%
7%
14%
Deaths Discharge Inpatients Other Unk

20. Update on September - November 2006
Outbreak in Pakistan
 Teaching Hospitals of
RMC reporting large
numbers
of patients seen in OPD
setting with unexplained
fever
 Suspect many cases are
being seen and managed
at primary care level

21. PAKISTAN: Eid travel bringsPAKISTAN: Eid travel brings
dengue fever Northdengue fever North
24 Oct 200624 Oct 2006 (( media headlinesmedia headlines))
The Pathology department atThe Pathology department at
Rawalpindi Medical College, close toRawalpindi Medical College, close to
the capital, Islamabad, expressedthe capital, Islamabad, expressed
apprehension that "as more and moreapprehension that "as more and more
people arrive from areas in Sindhpeople arrive from areas in Sindh
where the disease is endemic, there iswhere the disease is endemic, there is
a danger the epidemic will spread".a danger the epidemic will spread".

22. Mosquitoes spreading the disease have
ended up in buses trains and airplanes
heading north; or those
already infected with the virus in the
south have been bitten by local
mosquitoes at their destination, causing
the disease to spread further.

23. Till yesterday 8Till yesterday 8thth
November 2006November 2006
Reported Suspected cases in PakistanReported Suspected cases in Pakistan
32303230
ConfirmedConfirmed 11131113
Total Cases in the Twin Cities 500Total Cases in the Twin Cities 500
ConfirmedConfirmed 175175
Total deathsTotal deaths 3333
Cases being reported from Khushab ChakwalCases being reported from Khushab Chakwal
Pindi gheb Nowshera Peshawar Lahore etc.Pindi gheb Nowshera Peshawar Lahore etc.
( media reports)( media reports)

24. Disease PathogenesisDisease Pathogenesis

25. Replication and TransmissionReplication and Transmission
of 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

26. Transmission of Dengue VirusTransmission of Dengue Virus
byby Aedes aegyptiAedes 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

27. Neutralizing antibody to Dengue 1 virus
1
1
Dengue 1 virus1
Homologous Antibodies FormHomologous Antibodies Form
Non-infectious ComplexesNon-infectious Complexes
Non-neutralizing
antibody
1
1 Complex formed by neutralizing antibody
and virus

28. Replication and TransmissionReplication and Transmission
of 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

29. Risk Factors for DHFRisk Factors for DHF
(continued)(continued)
Higher risk in secondaryHigher risk in secondary
infectionsinfections
Higher risk in locations withHigher risk in locations with
two or more serotypestwo or more serotypes
circulating simultaneously atcirculating simultaneously at
high levels (hyperendemichigh levels (hyperendemic
transmission)transmission)

30. Hypothesis on PathogenesisHypothesis on Pathogenesis
of DHF (Part 1)of DHF (Part 1)
Persons who have experienced aPersons who have experienced a
dengue infection develop serumdengue infection develop serum
antibodies that can neutralize theantibodies that can neutralize the
dengue virus of that samedengue virus of that same
((homologoushomologous) serotype) serotype

31. Increased Probability of DHFIncreased 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

32. Hypothesis on PathogenesisHypothesis on Pathogenesis
of DHF (Part 2)of DHF (Part 2)
In a subsequent infection, the pre-In a subsequent infection, the pre-
existingexisting heterologousheterologous antibodiesantibodies
form complexes with the newform complexes with the new
infecting virus serotype, but do notinfecting virus serotype, but do not
neutralize the new virusneutralize the new virus

33. Non-neutralizing antibody to Dengue 1
virus
Dengue 2 virus
2 2
2
2
2
Heterologous AntibodiesHeterologous Antibodies
Form InfectiousForm Infectious
ComplexesComplexes
Complex formed by non-neutralizing
antibody and virus
2

34. 2
2
2
2
2
22
2
2
2
Heterologous Complexes EnterHeterologous Complexes Enter
More Monocytes, Where VirusMore Monocytes, Where Virus
ReplicatesReplicates
Non-neutralizing antibody
Dengue 2 virus2
Complex formed by non-
neutralizing antibody and
Dengue 2 virus
2

35. Hypothesis on PathogenesisHypothesis on Pathogenesis
of DHF (Part 3)of DHF (Part 3)
Antibody-dependent enhancementAntibody-dependent enhancement
is the process in which certainis the process in which certain
strains of dengue virus, complexedstrains of dengue virus, complexed
with non-neutralizing antibodies,with non-neutralizing antibodies,
can enter a greater proportion ofcan enter a greater proportion of
cells of the mononuclear lineage,cells of the mononuclear lineage,
thus increasing virus productionthus increasing virus production

36. DiagnosisDiagnosis

37. Key Lab. Diagnostic TestsKey Lab. Diagnostic Tests..
Virus isolation by infection of new-bornVirus isolation by infection of new-born
mice with blood or infected mosquitoesmice with blood or infected mosquitoes
PCRPCR
Detection of antigens or antibody to theDetection of antigens or antibody to the
agent in the blood (serology)agent in the blood (serology)
ELISA is availableELISA is available
ThrombopeniaThrombopenia
Raised hematocritRaised hematocrit
Decreased platelets and increase ALTDecreased platelets and increase ALT

38. Clinical laboratory testsClinical laboratory tests
– CBC--WBC, platelets, hematocritCBC--WBC, platelets, hematocrit
– AlbuminAlbumin
– Liver function testsLiver function tests
– Urine--check for microscopicUrine--check for microscopic
hematuriahematuria
Dengue-specific testsDengue-specific tests
– Virus isolationVirus isolation
– SerologySerology

40. Virus Isolation:Virus Isolation:
Cell CultureCell Culture

42. Recommendations for PreventionRecommendations for Prevention
and Controland Control
 Environmental assessment and vector controlEnvironmental assessment and vector control
– Vector surveillance and responseVector surveillance and response
Chemical, biologic methods, and personal protective measuresChemical, biologic methods, and personal protective measures
– Integrated management with community level involvementIntegrated management with community level involvement
– Health education at the communityHealth education at the community
 Emergency preparednessEmergency preparedness
– Hospital level plans to manage patientsHospital level plans to manage patients
 Capacity development and trainingCapacity development and training
– Vector controlVector control
– SurveillanceSurveillance
– Clinical managementClinical management
– Infection controlInfection control

43. In the battle against spread of Dengue virusIn the battle against spread of Dengue virus
biggest barrier seems is misinformation as well asbiggest barrier seems is misinformation as well as
ignorance,ignorance,
““The claim of National Institute of Health,The claim of National Institute of Health,
Islamabad, that not all labs can carry out theIslamabad, that not all labs can carry out the
diagnostic tests for Dengue is totally false and thediagnostic tests for Dengue is totally false and the
kit does not need the Bio-safety-level-3 protocol.”kit does not need the Bio-safety-level-3 protocol.”
Owing to confusion created by medical circles,Owing to confusion created by medical circles,
several private labs are charging thousands ofseveral private labs are charging thousands of
rupees for these tests, while they hardly costrupees for these tests, while they hardly cost
around Rs500-800 at the mainstream diagnosticaround Rs500-800 at the mainstream diagnostic
centers. Private hospital labs are said to becenters. Private hospital labs are said to be
charging around Rs3,000 for the same tests.charging around Rs3,000 for the same tests.

44. At many hospitals, patients are being keptAt many hospitals, patients are being kept
in isolation wards with the staff treatingin isolation wards with the staff treating
hem wearing masks and gloves which ishem wearing masks and gloves which is
also unnecessary.also unnecessary.
Generally GPs in the city start treating feverGenerally GPs in the city start treating fever
with anti-malarial or anti-biotic medicines,with anti-malarial or anti-biotic medicines,
while in an epidemic situation, allwhile in an epidemic situation, all
treatments should be followed by pre-treatments should be followed by pre-
testing to rule out the possibility oftesting to rule out the possibility of
contracting the disease that is spreading.contracting the disease that is spreading.
But this is usually not done and in someBut this is usually not done and in some
cases this negligence proves fatal.cases this negligence proves fatal.

45. At the same time, the anti-biotics and anti-malarialAt the same time, the anti-biotics and anti-malarial
drugs bear a serious toxic effect on bone marrow.drugs bear a serious toxic effect on bone marrow.
This impairs the production of white blood cellsThis impairs the production of white blood cells
(WBCs) and platelets.(WBCs) and platelets.
What is interesting is that the Dengue virus alsoWhat is interesting is that the Dengue virus also
acts in the same manner by killing WBCs andacts in the same manner by killing WBCs and
platelets. The combination of the two greatlyplatelets. The combination of the two greatly
worsens the condition.worsens the condition.
Dengue mosquito has certain peculiarDengue mosquito has certain peculiar
characteristics, which have serious implicationscharacteristics, which have serious implications
on Dengue Hemorrhagic Fever (DHF) control.on Dengue Hemorrhagic Fever (DHF) control.

46. A patched body which slightly differentA patched body which slightly different
from malarial mosquito, secondly, itfrom malarial mosquito, secondly, it
can transmit the disease with every bitecan transmit the disease with every bite
unlike the other which undergoes a 15-unlike the other which undergoes a 15-
day cycle of maturing before making itsday cycle of maturing before making its
bite lethal again.bite lethal again.
Worrisome is that the Aedes aegyptiWorrisome is that the Aedes aegypti
mosquito is a dawn-and-dusk-bitermosquito is a dawn-and-dusk-biter
when it is difficult to sense the bite.when it is difficult to sense the bite.
While window screening and bedWhile window screening and bed
netting may help until dawn, but mostlynetting may help until dawn, but mostly
people are outdoors at duskpeople are outdoors at dusk

47. Another problem : since it tends toAnother problem : since it tends to
breed inside closets, and in waterbreed inside closets, and in water
containers that are cool andcontainers that are cool and
covered, they are likely to findcovered, they are likely to find
opportune breeding ground insideopportune breeding ground inside
water storage tanks of houses aswater storage tanks of houses as
well as in institutions like prisons,well as in institutions like prisons,
hostels, hospitals, and schools.hostels, hospitals, and schools.
That is why clustering of cases isThat is why clustering of cases is
witnessed and it spreads like wildwitnessed and it spreads like wild
fire.fire.

48. ““It is wise to cover the body properly withIt is wise to cover the body properly with
clothing and apply mosquito repellantsclothing and apply mosquito repellants
adequately on the exposed skin surface. Anadequately on the exposed skin surface. An
ingredient in the repellants DEET actuallyingredient in the repellants DEET actually
works to keep these biters away becauseworks to keep these biters away because
with its peculiar odor.with its peculiar odor.
Mustard oil for its strong smell also servesMustard oil for its strong smell also serves
the same purpose,”the same purpose,”
The myths surrounding the reality of thisThe myths surrounding the reality of this
disease are making it all the more difficult todisease are making it all the more difficult to
deal with it, contend medical practitioners.deal with it, contend medical practitioners.
“Internationally, the mortality rate of DHF is“Internationally, the mortality rate of DHF is
hardly 2% while our data shows anhardly 2% while our data shows an
alarmingly high 5-10% only because ofalarmingly high 5-10% only because of
improper disease management,”improper disease management,”

49. Thank youThank you