Dengue is a viral infection transmitted by mosquitoes that infects around 100-400 million people annually worldwide. It is caused by the dengue virus of which there are 4 serotypes. Infection with one type provides lifelong immunity to that type but subsequent infections with other types increase the risk of severe dengue. The disease ranges from mild fever to life-threatening dengue hemorrhagic fever/dengue shock syndrome. There is no vaccine for dengue prevention currently.

1. Dengue
Dr. P K Maharana.

2. Introduction
• Dengue is a viral infection caused by the dengue virus
(DENV), transmitted to humans through the bite of
infected mosquitoes.
• About half of the world's population is now at risk of
dengue with an estimated 100–400 million infections
occurring each year.
• Dengue is found in tropical and sub-tropical climates
worldwide, mostly in urban and semi-urban areas.
• While many DENV infections are asymptomatic or
produce only mild illness, DENV can occasionally
cause more severe cases, and even death.

3. Epidemiology
• Dengue is a vector-borne viral disease caused by the flavivirus
dengue virus (DENV), they are of 4 sero types, infection with
one type gives life long immunity to the specific type, dose not
protect against other sub-types rather the severity increases.
• Caused due to mosquito bite, female , Aedes aegypti & Aedes
albopictus.
• Estimated that almost 400 million cases of dengue fever ( DF)
and half a million cases of dengue hemorrhagic fever (DHF)
occur worldwide, affecting half of the world’s population in 112
countries. Countries most affected USA, Africa, Australia, South
East Asia including India.
• Average case fatality rate is around 5% (22000).
• Up to 90% of patients with DHF are children less than 15 years ,
especially in South East and South Asia.

4. History
.
• The first dengue outbreak was reported in 1779 from Jakarta, (Indonesia)
and Cairo,( Egypt). In 1780 a report of outbreak was from North America,
the Philadelphia outbreak. (Rush 1951)
• The first two outbreak of Dengue Hemorrhagic fever ( DHF) was from
Manila in Philippines in 1953 & 1956, respectively.
• By 1975, dengue infections became a frequent cause of morbidity and
mortality particularly among the children in countries of South East Asia.
• In recent time, the largest outbreak of dengue, was in the year 2016, in
the USA, with more than 2.38 million cases reported. In this outbreak, the
highest contribution was from Brazil, with 1.5 million cases.
• In the last decade, epidemics caused by multiple serotypes
(hyperendemicity) have become increasingly frequent.
• Dengue has become one of the most important mosquito born viral
disease in the world.
• Apart from public health impacts it affects the economy to a very large
extent.

5. World prevalence of Dengue

6. Dengue in India
• The Indian subcontinent, owing to its suitable
environment, has several reports of dengue
outbreaks involving all serotypes. (Dar et al.
2006; Mustafa et al. 2015).
• A recent dengue epidemic was recorded in the
year 2017, where 1 88 401 infections and 325
deaths reported(NVBDCP).

7. Mode of transmission
• Transmission from human to human through mosquito
bite.( When a female Aedes Aegypti feeds on an infected
individual, along with blood it socks the virus, the virus
multiplies inside the mosquito and subsequently when the
mosquito bites a healthy individual the virus passes to the
human being present in the saliva)
• 1. Vector born – ( Commonest) Bite of an infected female
Aedes Aegypti mosquito.
• 2. Blood Born : ( Rarely)
• From infected pregnant mother to foetus.
• Blood Transfusion or organ transplantation.
• Needle Stick Injury.

8. Incubation Period
• Period of infectivity: An individual remains
infective during the period of viraemia, normally
it co-inside with period of fever, 2days before and
2 days after, usually 7 days.
• Extrinsic incubation period: It is the time when
the mosquito receives the virus through feed till
it secrets virus through saliva. It is roughly ( 8-12)
days.
• Intrinsic Incubation Period: ( 3-14 days), The
period from the entry of virus to clinical
manifestation.

9. Transmission from Mosquito to Human
• Transmission from mosquito to human beings : through the bites of
infected female mosquitoes, primarily the Aedes aegypti mosquito. Other
species within the Aedes genus can also act as vectors.
• After feeding on a DENV-infected person, the virus replicates in the
mosquito midgut before disseminating to secondary tissues, including the
salivary glands. Transmission occurs from saliva to the biting site on skin.
• The time it takes from ingesting the virus to actual transmission to a new
host is termed the extrinsic incubation period (EIP).
• The EIP takes about 8–12 days when the ambient temperature is between
25–28°C.
• Once infectious, the mosquito can transmit the virus for the
rest of its life.
• Human-to-mosquito transmission : Up to 2 days before
someone shows symptoms of the illness, and up to 2 days after
the fever has resolved.

10. Aedes aegypti
• Aedes aegypti are endophilic, occurring largely indoors, container-breeder.
(i.e., breeding in water-filled containers),
• A day-biting mosquitoes that feed preferentially on human blood under
field conditions and are found in tropical and subtropical areas, with their
geographic range spanning almost all continents (Thavara et al. 2001).
• Aedes albopictus, a more aggressive day-time biter, is exophilic under
natural field conditions, commonly living outdoors, but still feeds almost
exclusively on humans (Ponlawat and Harrington 2005; Delatte et al.
2010).
• The transmission of all four DENV serotypes is maintained in two cycles:
sylvatic (transmission in wild animals) and human (Chen and Vasilakis
2011)
• The sylvatic cycle is ecologically and evolutionarily distinct from the
human transmission cycle. This is maintained by non-human primates or
by a monkey-Aedes-monkey cycle in the sylvatic environments of
Southeast Asia, West Africa, peninsular Malaysia, and eastern Senegal
(Rudnick 1986).

11. Dengue Virus
Virus belonging to the genus Flavivirus.
• Consists of four closely related serotypes (DEN
1- 4) classified according to biological and
immunological criteria.
• The mature dengue virion consists of a
single-stranded RNA genome surrounded by
an icosahedral or isometric nucleocapsid.
• This nucleocapsid is covered by a lipid
envelope.

12. Virus Morphology
 A complete virion is about 50 nm in diameter and the viral
genome is approximately 11 kb in length.
 A well-organized outer protein layer on the surface of a lipid bilayer,
and an inner nucleocapsid core.
 DENV contains three structural proteins, namely, the capsid (C),
membrane (M) (having a membrane precursor or PrM), envelope
(E), and seven non-structural proteins (NS1, NS2A, NS2B, NS3,
NS4A, NS4B, and NS5) .
 Envelope proteins carries out biological functions of the virus----
1.)-Transport of the viral genome into the host cell.
2.)- Haemagglutination of erythrocytes
3.)-Induction of neutralizing antibodies
4)-Protective immune responses.

13. Electron Microscopic Structure

14. Pathogenesis
Most important changes:
 ↑Vascular permeability,
 ↑Thrombocytopaenia,
 ↑Coagulopathy.
 Complement activation &
 Hepatomegaly

15. Antibody-dependent enhancement
• After a primary infection with a DENV serotype, the
immune system produces antibodies that bind and
neutralize secondary infection with the same serotype,
however, a secondary heterotypic infection may lead to
enhance severity.
• The antibodies produced from the primary infection have
the ability to bind to the virus but lack the ability to
neutralize.
• These cross-reactive antibodies form infectious virus-
antibody complexes are able to bind and enter in cells that
present the Fcγ-receptors such as, monocytes,
macrophages, and dendritic cells, therefore, enhancing viral
production leading to higher viral loads.

16. Antibody Dependant Reaction

17. Cytokine dysregulation
• In the development of DHF, DENV antibodies may
be unable to neutralizing and alternatively
promote the entrance of a second serotype of
DENV into Fcγ-expressing cells, which results in
amplified activation of complements and rapidly
produces cytokine. (especially pro-inflammatory
type 1 cytokines, such as TNF-α and IFN-γ).
• These cytokines may have a direct effect
on vascular endothelial cells leading plasma
leakage.

18. Causes of thrombocytopenia
• Destruction of Platelets (Circulating Platelet
antibodies ).
• Bone marrow suppression.
• DIC
• Peripheral sequestration of platelets.

19. Dengue Fever
• DF: is an acute infectious disease symptom,
characterized by biphasic fever, myalgia, headache,
joint pain, retro-orbital pain, body rash,,
lymphadenopathy, thrombocytopenia and leukopenia.
• Dengue fever has three distinct phases:
– febrile, critical, and convalescent.
• The febrile phase is characterized by a sudden high-
grade fever and dehydration that can last for 2–7 days.
• The convalescence period is the recovery phase, when
rash, itching, and increased appetite are observed.

20. Symptoms
• If symptoms occur, they usually begin 4–10 days after
infection and last for 2–7 days. Symptoms may include:
• high fever (40°C/104°F)
• severe headache
• pain behind the eyes
• muscle and joint pains
• nausea
• vomiting
• swollen glands
• rash.

21. Dengue Fever Cycle.
• Fever 2-3 days
• Critical period 4-5-6 day
• Recovery 7th day onwards.

22. Life cycle of Dengue Fever

23. Severe Dengue
• Severe dengue symptoms often come after the fever has
gone away:
• Severe abdominal pain
• Persistent vomiting
• Rapid breathing
• Bleeding gums or nose
• Fatigue
• Restlessness
• Blood in vomit or stool
• Being very thirsty
• Pale and cold skin
• Feeling weak.

24. DHF & DSS
• DHF as prescribed by the WHO are acute and
continuous fever of 2–7 days, hemorrhage
associated with thrombocytopenia (100 000
cells/cu. mm or less), and haemoconcentration
(Haematocrit >20% from baseline of patients of
the same age).
• DSS: Presents with shock like features (Hypo
volaemic shock), multi organ failure, along with
any of the above features.

25. DHF
• High grade fever lasting for 2-7 days( > 104 F).
• Any hemorrhagic manifestations. ( Positive
tourniquet test, Epistaxis, bleeding gum, petechiae on
skin)
• Low platelet count ( < 1,00,000 mm3).
• Evidence of increased vascular permeability (
Low BP, High low volume Pulse , breathing difficulty,
altered sensation)

26. Risk Factors
• Previous infection with DENV increases the risk of
the individual developing severe dengue.
• Urbanization (especially unplanned, is associated with
dengue transmission through multiple social and
environmental factors): Population density, human mobility,
access to reliable water source, water storage practice etc.
• Environmental Factors: Climate Change

27. Risk Factors with DHF

28. DSS ( Dengue Shock Syndrome)
 Any case that meets the four criteria of DHF ,
and has evidence the features of circulatory
failure.
Rapid weak pulse, Low BP, restlessness, cold
clammy skin.
• DSS is a severe condition if not treated properly
death in 10% cases, with proper treatment
mortality reduced to 1%.

29. DSS (Dengue Shock Syndrome)
• It develops mostly after 3-5 days of fever.
• Hypotension and multi organ dysfunction.
• Low Platelet count.
• Bleeding diathesis.
• Dyspnoea (Fluid in Pleural and peritoneal space).
• Cardiac Failure & Death.
• DHF are still yet fully understood.
 Currently proposed risk factors correlated with DHF
include virus virulence,10 immune enhancement,11 cytokine
storm,12 change of lipid profile,13 autoimmune
responses,14 host genetic factors,15 bacteremia caused
by Staphylococcus aureus16,17 etc.

30. Evidence of Plasma Leakage
Evidence of plasma leakage due to increased vascular
permeability consists of at least one of the followings.
• An elevated ↑ hematocrit ≥20% above the
population mean hematocrit for age and sex.
• A decline in ↓hematocrit after volume-replacement
treatment of ≥20% of the baseline hematocrit.
• Presence of pleural effusion or ascites detected by
radiography or other imaging method.
• Hypoproteinemia or hypoalbuminemia as
determined by laboratory test.

31. Monitoring
• Look for the evidence of
• Hemorrhage.
• Capillary Leak ( Ascites, pleural effusion )
• Monitor: Para meters to be monitored.
 Pulse ( Thready low volume pulse),
 Blood Pressure,
 Urine output ( should be between 0.5 -1ml/kg/hour).
 Haematocrit & Platelet Count.

32. Differential Diagnosis
• Dengue fever can easily be confused with
non-dengue illnesses, depending on the
geographical origin of the patient, other
etiologies – including
• Non-dengue flavivirus infections – should be
ruled out. These include yellow fever, Japanese
encephalitis, St Louis encephalitis, Zika, and West Nile,
alphaviruses (such as Sinbis and chikungunya),
• Other causes of fever- such as malaria,
leptospirosis, typhoid, Rickettsial diseases

33. Differential Diagnosis
• Flue, Measles,
• Malaria, Typhoid, Scrub Typhus,

34. Laboratory Tests
• Presence of virus – RT-PCR ( within 24 hours to
5days)
• Viral Antigen -( NS1)
• Antibody against virus- IgM & IgG( From 6 days
onwards)

35. Blood Samples
• Blood Samples ( Serum) .
• For RT-PCR ( Stored at 4C for a week, dry ice
if for a longer duration)
• For Antibodies in a closed container,( avoid
exposure to high temperature , ice in the box )

36. Diagnosis

37. Diagnosis
• Examination of Blood to detect viral antigen
particle or antibodies.
• NS1 antigen assay, usually positive within 1st
week ( 3-9. days).
• Dengue IgM / IgG serological test ( Both Card &
ELISA), it is only positive after 5th Day.
 ELISA are the tests of choice after the first five
days of illness. Immunoglobulin M (IgM) or
immunoglobulin G ( IgG) are detected by enzyme-linked
immunosorbent assay (ELISA).

38. During Febrile Period ( Before 5 Days)
 1). Virus isolation in cell culture.
 2). Detection of viral RNA by nucleic acid
amplification tests (NAAT).
 3). Detection of viral antigens by ELISA or rapid
tests.

39. NSN 1 antigen
• NSN 1 antigen ( Viral antigen) is a non structural viral
protein secreted by the infected cells.
• After the onset of illness, the virus can be detected in
serum, plasma, circulating blood cells and other
tissues for 4–5 days.
• So, in early phase, detection of viral antigen
is diagnostic.

40. Antibodies
• IgM antibodies are the first immunoglobulin isotype to
appear.
• These antibodies are detectable in 50% of patients by
days 3-5 after onset of illness, increasing to 80% by day 5 and
99% by day 10 .
• IgM antibodies levels peak about two weeks after the
onset of symptoms and then decline generally to undetectable
levels over 2–3 months.
• IgG antibodies are generally detectable at low titers at the
end of the first week of illness, increasing slowly thereafter,
with serum IgG still detectable after several months, and
probably even for life .

41. Diagnosis
 Direct Method: Virus Isolation, Genome detection,
NS1 detection.
 Indirect Method : Antibody Detection (IgM & IgG )
Virus isolation and nucleic acid detection: are
more labour-intensive and costly but are also more specific
than antibody detection using serologic methods.

42. Different Tests Recommended
• Virus Isolation
• Nucleic Acid detection
• RT-PCR
• Detection of Antigen
• Serological Tests ( MAC-ELISA)
• Haematological Tests: ( Haematocrit, Platelet
Count)

43. How to differentiate between primary
& secondary infection?
• 1. In secondary infection IgG is strongly
positive.
• 2. IgM may be negative or in low titer,
• 3. NSN 1 antigen positive.
• 4. IgM/IgG ratio:
• > 1.2 Primary
• < 1.2 Secondary

44. Treatment
• Rest
• Drink plenty of liquids
• Use acetaminophen (paracetamol) for pain
• Avoid non-steroidal anti-inflammatory drugs,
like ibuprofen and aspirin.
• Watch for severe symptoms and contact your
doctor as soon as possible if you notice any

45. Laboratory findings
• Laboratory findings in the febrile phase
include the following:
• Leukopenia
• Mild to moderate thrombocytopenia
• Elevated aspartate aminotransferase (AST)
• Elevated alanine aminotransferase (ALT)
• Hyponatremia

46. Medical complications during Febrile
Phase
• Dehydration
• Hyponatremia
• Febrile seizures in young children
• Neurologic disease manifestations,
including encephalitis and aseptic meningitis.

47. Severe Dengue
 Patients are considered to have severe dengue if they meet any of
the following three criteria.
 1. Severe plasma leakage resulting in one or both of the following:
– Shock
– Fluid accumulation with respiratory distress
 2. Severe bleeding as evaluated by clinician
 3. Severe organ involvement
 Hepatic (involving the liver): AST or ALT level > 1000 U/L
 Neurologic (involving the central nervous system): impaired consciousness
 Myocardial (involving the heart) and
 Other organs

48. Pathogenesis of Severe Dengue
• Severe dengue most commonly occurs among patients with secondary DENV
infections and infants with primary infections. The most widely-cited hypothesis
for the pathogenesis of severe dengue is antibody-dependent enhancement
(ADE).
• Although the exact mechanisms are not clear, ADE is the process in which DENV,
complexed with nonneutralizing antibodies, can enter a greater proportion of cells
of the mononuclear lineage, thus increasing virus production.
• Antibodies typically protect humans from viruses in 3 ways
– neutralization (antibody blocks virus interaction with host cell)
– opsonization (antibody coats virus and typically targets it for uptake by macrophages and
neutrophils)
– antibody-dependent cellular cytotoxicity (ADCC)
• In dengue, nonneutralizing heterotypic IgG anti-DENV antibodies produced during
a person's first DENV infection (or sub-neutralizing level of antibodies in the case
of infants who acquired IgG passively in utero) can form antibody-DENV complexes
in the second infection that can allow uptake of DENV by macrophages. DENV then
replicates in these macrophages thereby increasing viral production.

49. Risk Factors for Severe Dengue
• Not all dengue cases are severe.
• Approximately 10% of dengue cases progress to
severe disease, independent of treatment.
• Physicians might be able to prevent and treat
medical complications such as fluid overload.
• Factors have been identified that are associated
with an increased risk for severe disease, but
there are no tests or biomarkers to identify which
patients, when presenting early in the course of
disease, will develop severe disease.

50. Critical phase
The critical phase typically begins around the time of
defervescence but it might begin as early as the third
day after fever onset in patients who are still febrile.
• This is the period when those who develop severe
disease will become critically ill.
Onset of the critical phase can also be identified by
the following:
 1.Rapid decline in platelet count with a rise in
hematocrit (HCT)
 2.The patient might develop leukopenia up to 24 hours
before platelet drop is recognized.
 3.Presence of warning signs for severe disease

51. Warning Signs
Warning signs include the following:
• 1. Clinical fluid accumulation, such
as ascites, pleural effusion.
• 2. Liver enlargement > 2 cm.
• 3. Severe abdominal pain.
• 4. Persistent vomiting (at least 3 vomiting.
episodes within 24 hours).
• 5. Mucosal bleed.
• 6. Lethargy or restlessness.

52. Medical complications during Critical
Phase
Include the following:
• Hypovolamic shock from plasma leakage
• End organ impairment due to prolonged shock
• Severe hemorrhage
• Encephalopathy

53. Recovery
 Recovery depends on the severity of the illness and any
treatments prescribed in the febrile and critical phases.
Onset of the recovery phase can be identified by the
following:
 Features of improvement.
• Gradual reabsorption of extravasated fluid (such as from
plasma leakage) over 48–72 hours.
• Increased diuresis (patient might wet bed).
• Hemodynamic status stabilizes.
• Patient can temporarily become bradycardic (but
haemodynamically stable).

54. Clinical manifestations
 Clinical manifestations during the recovery phase include
the following:
• A second rash that might be macular or erythematous with
small circular islands of normal, unaffected skin. This
convalescent rash can be very pruritic and desquamate.
• Severe fatigue.
• Laboratory findings in the recovery phase include the
following:
• HCT stabilizes or is slightly lower due to a dilutional effect
of reabsorbed plasma (hemodilution).
• White blood count (WBC) begins rising soon after
defervescence.
• Platelet count increases following WBC recovery.

55. Causes of Death
Severe dengue can result in death. Causes of
death from dengue include the following:
• Unrecognized dengue without appropriate
medical management.
• Unrecognized or prolonged shock.
• Unrecognized occult hemorrhage.
• Fluid overload.
• Nosocomial infections.
• Liver failure.

56. The 2009 WHO guidelines emphasize the importance of
detecting clinically significant plasma leakage early.

57. Close Monitoring of Vital Parameters
• Level of consciousness (Use GCS.)
• Skin temperature, color, and moisture level (normal, dry or
clammy)
• Peripheral pulse volume/Capillary refill
• Heart rate
• Blood pressure
• Respiratory rate
• Urine output
 Early signs of shock include:
 Narrowing of pulse pressure (PP) with rising diastolic blood
pressure (DBP)
 Delayed capillary refill (> 2 seconds)
 Tachycardia in absence of fever

58. Group A patients
• Rest
• Rehydration
• Paracetamol for fever.
• Do not give corticosteroids to patients with
dengue.
• Do not give NSAIDS, for example acetyl- salicylic
acid (aspirin) and ibuprofen.
• Do not give antibiotics, unless there is a clinical
suspicion of leptospirosis or of a dual infection.

59. Management in group B patients
Group B and C patients require hospital monitoring
and treatment. These patients require the following
interventions:
• Monitoring hemodynamic status and tracking intake and output
• Use of HCT to guide interventions
• Use isotonic intravenous fluids (IVFs) to restore plasma volume
• Monitoring for signs of occult bleeding
• Use of blood products as needed
• Correction of metabolic acidosis, use of electrolytes as needed
• Use of colloids for refractory shock

60. How to calculate Hypotension in <
10yrs of age.
• Hypotension in patients younger than 10 years
old is defined by a SBP of less than 70 + (2
times the patient age in years).

61. Dengue Cases with Plasma Leak

62. Treatment of Hemorrhage
• Packed red blood cells (PRBC) or whole blood (if volume is
not an issue for the patient) should be given to dengue
patients who have clinically significant occult or overt
hemorrhage.
•
• Give 5–10 mL/kg of PRBC or 10–20 mL/kg of whole blood at
appropriate rate and observe the clinical response.
• Consider repeating the blood transfusion, if
– There is further blood loss.
– There is no appropriate increase in HCT after blood
transfusion. For instance, an appropriate increase is 3%–4% rise
in HCT for every 10 cc/kg of PRBC given.

63. Vaccine
• A vaccine called Dengvaxia recommended for
people who have had dengue at least once and
live in places where the disease is common.
• So far only one vaccine (Dengvaxia) has been
approved and licensed in some countries.
• Several additional dengue vaccine candidates are
under evaluation.
• Dengue vaccine is only for people showing
positive past infection and remaining dengue
endemic region.

64. Prevention
To lower the risk of getting dengue by protecting
yourself from mosquito bites by using:
• 1.Clothes that cover as much of your body as possible
• 2.Mosquito nets if sleeping during the day, ideally
nets sprayed with insect repellent.
• 3.Window screens.
• 4.Mosquito repellents (Containing DEET, Picaridin or
IR3535) coils and vaporizers.
The mosquitoes that spread dengue are active during
the day.