1. Dr. Keerti Singh Assistant Professor SGRRITS
Dengue
Dr. Keerti Singh
Assistant Professor
SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences 1

2. Dengue Virus (Arbovirus)
Causes dengue and dengue hemorrhagic fever
Transmitted by mosquitoes
Composed of single-stranded RNA
Has 4 serotypes (DEN-1, 2, 3, 4)
Each serotype provides specific lifetime immunity, and short-term cross-immunity
All serotypes can cause severe and fatal disease
Genetic variation within serotypes
Some genetic variants within each serotype appear to be more virulent or have greater epidemic potential
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences 3

3. Transmission of Dengue Virus (Through Vector i.e Mosquito)
Dr. Keerti Singh, Assistant Professor, SGRRITS

4. Aedes aegypti
The most common epidemic vector of dengue in the world is the Aedes aegypti mosquito. It can be identified by the white bands or scale patterns on its legs and thorax.
Dengue transmitted by infected female mosquito
Primarily a daytime feeder
Lives around human habitation
Lays eggs and produces larvae preferentially in artificial containers
Dr. Keerti Singh, Assistant Professor, SGRRITS

5. Dr. Keerti Singh, Assistant Professor, Division of Life Sciences
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

6. One mosquito bite can inflict the disease.
The mosquito flourishes during rainy seasons but can breed in water-filled flower pots, plastic bags, and cans year-round.
One mosquito bite can inflict the disease.
Under optimal conditions, the egg of an Aedes mosquito can hatch into a larva in less than a day.
The larva then takes about four days to develop in a pupa, from which an adult mosquito will emerge after two days.
Three days after the mosquito has bitten a person and taken in blood, it will lay eggs, and the cycle begins again.
Dr. Keerti Singh, Assistant Professor, SGRRITS

7. Facts about the mosquito
Only the female Aedes mosquito bites as it needs the protein in blood to develop its eggs.
The mosquito becomes infective approximately 7 days after it has bitten a person carrying the virus.
This is the extrinsic incubation period, during which time the virus replicates in the mosquito and reaches the salivary glands.
Dr. Keerti Singh, Assistant Professor, SGRRITS

8. The average lifespan of an Aedes mosquito in Nature is 2 weeks.
The mosquito can lay eggs about 3 times in its lifetime, and about 100 eggs are produced each time.
The eggs can lie dormant in dry conditions for up to about 9 months, after which they can hatch if exposed to favourable conditions, i.e. water and food.
Dr. Keerti Singh, Assistant Professor, SGRRITS

9. Transmission of Dengue Virus by Aedes aegypti
Dr. Keerti Singh, Assistant Professor, SGRRITS

10. Virus transmitted to human in mosquito saliva
Replication and Transmission of Dengue Virus
Virus transmitted to human in mosquito saliva
Virus replicates in target organs
Virus infects white blood cells and lymphatic tissues
 Virus released and circulates in blood
Dr. Keerti Singh, Assistant Professor, SGRRITS

11. Virus replicates in salivary glands
Replication and Transmission of Dengue Virus
Second mosquito ingests virus with blood
Virus replicates in mosquito midgut and other organs, infects salivary glands
Virus replicates in salivary glands 
Dr. Keerti Singh, Assistant Professor, SGRRITS

12. DENGUE VIRUS INFECTION
Asymptomatic
Symptomatic
Dengue Haemorrhagic fever
Undiffrentiated fever
(viral syndrome)
Dengue fever
(syndrome)
(Plasma leakage)
Dengue Fever
Dengue Shock Syndrome (DSS)
No Shock
Dengue Haemorrhagic fever
Dr. Keerti Singh, Assistant Professor, SGRRITS

13. There are actually four dengue clinical syndromes:
Undifferentiated fever;
Classic dengue fever;
Dengue hemorrhagic fever, or DHF; and
Dengue shock syndrome, or DSS.
Dengue shock syndrome is actually a severe form of DHF.
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

14. Clinical Case Definition for Dengue Fever
Classical Dengue fever or Break bone fever is an acute febrile viral disease frequently presenting with headaches, bone or joint pain, muscular pains,rash,and leucopenia
Clinical Case Definition for Dengue Hemorrhagic Fever
4 Necessary Criteria:
Fever, or recent history of acute fever
Hemorrhagic manifestations
Low platelet count (100,000/mm3 or less)
Objective evidence of “leaky capillaries:”
elevated hematocrit (20% or more over baseline)
low albumin
pleural or other effusions
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

15. Clinical Case Definition for Dengue Shock Syndrome 4 criteria for DHF +
Evidence of circulatory failure manifested indirectly by all of the following:
Rapid and weak pulse
Narrow pulse pressure (< 20 mm Hg) OR hypotension for age
Cold, clammy skin and altered mental status
Frank shock is direct evidence of circulatory failure
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

16. Hemorrhagic Manifestations of Dengue
Skin hemorrhages: petechiae, purpura, ecchymoses
Gingival bleeding
Nasal bleeding
Gastrointestinal bleeding: Hematemesis, melena, hematochezia
Hematuria
Increased menstrual flow
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

17. Signs and Symptoms of Encephalitis/Encephalopathy Associated with Acute Dengue Infection
Decreased level of consciousness: lethargy, confusion, coma
Seizures
Nuchal rigidity
Paresis
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

18. Four Grades of DHF Grade 1
Fever and nonspecific constitutional symptoms
Positive tourniquet test is only hemorrhagic manifestation
Grade 2
Grade 1 manifestations + spontaneous bleeding
Grade 3
Signs of circulatory failure (rapid/weak pulse, narrow pulse pressure, hypotension, cold/clammy skin)
Grade 4
Profound shock (undetectable pulse and BP)
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

19. Danger Signs in Dengue Hemorrhagic Fever
Abdominal pain - intense and sustained
Persistent vomiting
Abrupt change from fever to hypothermia, with sweating and prostration
Restlessness or somnolence
*All of these are signs of impending shock and should alert clinicians that the patient needs close observation and fluids.
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

20. Dr. Keerti Singh, Assistant Professor, Division of Life Sciences
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

21. This thermometer illustrates the developments in the illness that are progressive warning signs that DSS may occur.
The initial evaluation is made by determining how many days have passed since the onset of symptoms.
Most patients who develop DSS do so 3-6 days after onset of symptoms. Therefore, if a patient is seven days into the illness, it is likely that the worst is over.
If the fever goes between three and six days after the symptoms began, this is a warning signal that the patient must be closely observed, as shock often occurs at or around the disappearance of fever.
Other early warning signs to be alert for include a drop in platelets, an increase in hematocrit, or other signs of plasma leakage.
If you document hemoconcentration and thrombocytopenia and other signs of DHF and the patient meets the criteria for DHF, the prognosis and the patient's risk category have changed. Though dengue fever does not often cause fatalities, a greater proportion of DHF cases are fatal.
The next concern would be observation of the danger signs—severe abdominal pain, change in mental status, vomiting and abrupt change from fever to hypothermia. These often herald the onset of DSS.
The goal of treatment is to prevent shock. The plasma leakage syndrome is self-limited. If you can support the patient through the plasma leakage phase and provide sufficient fluids to prevent shock, the illness will resolve itself.
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

22. Dr. Keerti Singh, Assistant Professor, Division of Life Sciences
Dr. Keerti Singh, Assistant Professor, SGRRITS
Dr. Keerti Singh, Assistant Professor, Division of Life Sciences

23. Homologous Antibodies Form Non-Infectious Complexes1
Dr. Keerti Singh, Assistant Professor, SGRRITS

24. Heterologous Antibodies Form Infectious Complexes
                                                                                      2
Dr. Keerti Singh, Assistant Professor, SGRRITS

25. Heterologous Complexes Enter More Monocytes, Where Virus Replicates3
Dr. Keerti Singh, Assistant Professor, SGRRITS

26. Petechiae Dr. Keerti Singh, Assistant Professor, SGRRITS
                            
View enlarged image
                           
Dr. Keerti Singh, Assistant Professor, SGRRITS

27. Tourniquet Test
The tourniquet test assesses capillary fragility. You inflate the blood pressure cuff to a point midway between the systolic and diastolic blood pressures for five minutes. After deflating the cuff, wait for the skin to return to its normal color, and then count the number of petechiae visible in a one-inch-square area on the ventral surface of the forearm. Twenty or more petechiae in the one-inch square patch constitutes a positive test.
Dr. Keerti Singh, Assistant Professor, SGRRITS

28. Virus Isolation: Cell Culture
mosquito cell cultures -blood sample are positive: the fluorescing cells seen
here are infected with dengue virus.
Dr. Keerti Singh, Assistant Professor, SGRRITS

29. Virus Isolation: Mosquito Inoculation
Dr. Keerti Singh, Assistant Professor, SGRRITS

30. ELISA Plate
The ELISA detects the presence of anti-dengue IgM in a patient's blood sample, indicating a recent dengue infection.
The more intense the color reaction, the greater the level of anti-dengue IgM antibody in the sample.
Dr. Keerti Singh, Assistant Professor, SGRRITS

31. Dr. Keerti Singh, Assistant Professor, SGRRITS

32. Dr. Keerti Singh, Assistant Professor, SGRRITS

33. Dr. Keerti Singh, Assistant Professor, SGRRITS

34. Dr. Keerti Singh, Assistant Professor, SGRRITS

35. A TEM micrograph showing Dengue virus virions (the cluster of dark dots near the center).
Dr. Keerti Singh, Assistant Professor, SGRRITS