Dengue - Nelson 21 Flashcards
Characteristics of dengue fever
Biphasic fever Myalgia / arthralgia Rash Leukopenia Lymphadenopathy
Characteristics of dengue hemorrhagic fever
Capillary permeability
abnormalities of hemostasis
Severe: protein-losing shock syndrome DSS
Severe dengue includes
Fluid loss leading to shock Fluid loss w respi distress Liver damaged (^ALT AST >100U/L) Severe bleeding Altered consciousness Significant heart abnormalities
Family of dengue virus
Flaviviridae
Dengue like diseases and their virus
Chikungunya - Togavirus
O’nyong-nyong - Togavirus
West nile fever - Flavivirus
Principal Vector of Dengue
Mosquito - Stegomyia family, Aedes aegypti
Where does A. aegypti breeds
Water stored for drinking and rainwater collected in a y container
These species breed in water trapped in vegetation; caused of Hawaiian epidemics
Aedes albopictus
Explain the urban transmission cycle
viremic humans –> bitten by vector mosquito –> virus multiplies during extrinsic incubation period –> bite is passed on to a susceptible human
Since A. aegypti has limited flight ranged, spread of the virus is possible through?
through viremic human beings and follows the main lines of transportation
Dengue-like diseases may occur in epidemics. Epidemiologic features depend on what 2 factors?
vectors
their geographic distribution
Occurs where multiple types of dengue virus are simultaneously or sequentially transmitted. It is endemic in tropical America, Asia, the Pacific Islands, and parts of Africa, where warm temperatures and the practices of water storage in homes plus outdoor breeding sites result in large, permanent populations of A. aegypti
Dengue Hemorrhagic Fever
In areas of high endemicity, this infections are frequent.
secondary infections
This infection is relatively mild in the majority of instances, ranging from an inapparent infection through an undifferentiated upper respiratory tract or dengue-like disease, but may also progress to dengue
hemorrhagic fever
Secondary dengue infections
Dengue hemorrhagic fever can occur during primary dengue infections, most frequently in ?
Infants whose mothers are immune to dengue
Dengue hemorrhagic fever or severe dengue occurs rarely in individuals of what ancestry because of an as yet incompletely described resistance gene
African ancestry
Pathogenesis of DHF
usually associated with second heterotypic infections with dengue types 1-4 or
in infants born to mothers who have had two or more lifetime dengue infections
Retrospective studies of sera from human mothers whose infants acquired DHF and in children acquiring sequential dengue infections have shown that the circulation of ___ at the time of infection is the strongest risk factor for development of severe disease
infection-enhancing antibodies
best correlates of risk for dengue hemorrhagic fever
(-) crossreactive neutralizing antibodies
(+) enhancing antibodies from passive transfer or active production
Pathology of Dengue
When dengue virus immune complexes attach to monocyte/macrophage Fc receptors, a signal is sent that suppresses innate immunity, resulting in enhanced viral production
In the Americas, DHF and DSS have been associated with these strains of recent Southeast Asian origin
dengue types 1-4 strains
Outbreaks of DHF in all areas of the world are correlated with___ while recent outbreaks in India, Pakistan, and Bangladesh are related to ___
secondary dengue infections
imported dengue strains
Early in the acute stage of secondary dengue infections, there is rapid activation of ___
complement system
Shortly before or during shock, blood levels of these (3) are elevated
soluble tumor necrosis factor receptor
interferon-γ
interleukin-2
These are depressed at times of DHF
C1q, C3, C4, C5-C8, and C3 proactivators are depressed
Catabolic rates of these are elevated
C3 catabolic rates are elevated
This is a viral toxin that activates myeloid cells to release cytokines by attaching to toll receptor 4. It also contributes to increased vascular permeability by activating complement, interacting with and damaging endothelial cells, and interacting with blood clotting factors and platelets
Circulating viral nonstructural protein 1 (NS1)
Capillary damage allows fluid, electrolytes, small proteins, and, in some instances, RBC to leak into extravascular spaces. This internal
redistribution of fluid, together with deficits caused by fasting, thirsting, and vomiting, results in ____ (6)
hemoconcentration hypovolemia increased cardiac work tissue hypoxia metabolic acidosis hyponatremia
In rare instances, death may be a result of
gastrointestinal or intracranial hemorrhages
Pathologic lesion in GI tract (death)
Minimal to moderate hemorrhages are seen in the upper gastrointestinal tract
Pathologic lesion in the heart (death)
petechial hemorrhages are common in the interventricular septum and pericardium
Pathologic lesion in the liver (death)
usually enlarged, often with fatty changes
Incubation period of Dengue fever
1-7 days
CM in infants and young children
fever for 1-5 days
pharyngeal inflammation
rhinitis
mild cough
CM in older children and adults
Sudden onset of fever (39.4 - 41.1°C)
frontal or retroorbital pain,
occasionally, severe back pain precedes the fever (back-break fever)
may be seen during the first 24-48 hr of dengue fever
transient, macular, generalized rash that blanches under pressure
pulse rate may be slow
myalgia and arthralgia occur soon after the onset of fevers and increase in severity
2nd to 6th day of dengue fever
fever nausea vomiting generalized lymphadenopathy cutaneous hyperesthesia or hyperalgesia taste aberrations pronounced anorexia
1-2 days after defervescence, what is seen in dengue fever and disappears after how many days?
a generalized, morbilliform, maculopapular rash appears that spares the palms and soles
1-5 days
Rarely there is _____ of the palms and soles.
About the time this second rash appears, the body temperature, which has previously decreased to normal, may become slightly elevated and demonstrate the characteristic _____
edema
biphasic temperature pattern
Describe the first phase of Dengue Hemorrhagic Fever and Dengue Shock Syndrome (DHF/DSS)
Mild first phase with abrupt onset of fever malaise vomiting headache anorexia cough may be followed after 2-5 days by rapid clinical deterioration and collapse
In rapid clinical deterioration and collapse in DHF/DSS or the second phase, the patient usually has
cold, clammy extremities warm trunk flushed face diaphoresis restlessness irritability midepigastric pain decreased urinary output
In second phase of DHF/DSS, skin is affected by
scattered petechiae on the forehead and extremities spontaneous ecchymoses
easy bruising and bleeding at sites of venipuncture
macular or maculopapular rash
circumoral and peripheral cyanosis
In second phase of DHF/DSS, lungs is affected by
Respirations are rapid and often labored
In second phase of DHF/DSS, heart is affected by
Pulse is weak, rapid, and thready
heart sounds are faint
In second phase of DHF/DSS, liver is affected by
Liver may enlarge to 4-6 cm below the costal margin and is usually firm and somewhat tender
Approximately 20– 30% of cases of dengue hemorrhagic fever are complicated by
shock (dengue shock syndrome)
Dengue shock can be subtle, arising in patients who are fully alert, and is accompanied by (2)
increased peripheral vascular resistance
raised diastolic blood pressure
(DHF/DSS) Shock is not from congestive heart failure but from
venous pooling
(DHF/DSS) With increasing cardiovascular compromise, the diastolic pressure _____ the systolic level and the _____ narrows
diastolic pressure RISES TOWARD the systolic level pulse pressure narrows
(DHF/DSS) In uncorrected shock, <10% of patients usually have (2)
gross ecchymosis or gastrointestinal bleeding
(DHF/DSS) After a 24- to 36-hr period of crisis,
convalescence is fairly rapid in the children who recover. The temperature may return to normal before or during the stage of shock. _____ and _____ are common during convalescence.
Bradycardia and ventricular extrasystoles
Clinical diagnosis derives from these 2 factors
High index of suspicion
Knowledge on geographic distribution and environmental cycles of causal virus s
This term should be used until a specific diagnosis of dengue is established
Dengue-like diseases
Dengue Case is confirmed through (3)
1 Isolation of virus viral antigen and genome by PCR analysis
2 IgM dengue antibodies detection
3 4 fold increase in antibody titers
WHO criteria for DHF
1 Fever (2-7d biphasic) 2 Minor or major hg manif (6) Tourniquet test positive Thrombocytopenia <100,000/uL Hct >20% (inc cap perm) Pleural effusion Ascites Hypoalbuminemia
DSS criteria
DHF criteria Hypotension Tachycardia Narrow pulse pressure =20mmHg Poor perfusion (cold extremities)
Probable dengue
Live/ travel to endemic area Fever and 2 of ff 1 NAusea 2 Rash 3 Aches and pains 4 TT positive 5 Leukopenia 6 Any warning sign
Dengue with warning signs
Abdominal pain or tenderness Persistent vomiting Mucosal bleed Clinical fluid accumulation Lethargy, restlessness Liver enlargement >2cm Labs -inc in Hct w rapid dec in platelets
Severe dengue
Severe plasma leakage
Shock DSS
Fluid accumulation w Respi distress
Severe bleeding
as evaluated by clinician
Severe organ involvement
Liver AST or ALT >/= 1000
CNS Altered consciousness
Heart other organs
Virologic dx can be established by serologic tests by (2)
Detection of viral proteins or viral RNA
Isolation of virus from blood leukocytes or acute phase serum
Following primary and secondary infections, there is an appearance of what Antibodies that disappears after 6-12wks a feature that can be used to date a dengue infection
Antidengue IgM antibodies
In secondary infections most dengue antibody is this and serologic studies depends on four fold increase in this antibody titer
IgG
IgG antibody titer
This is a viral nonstructural protein released by infected cells into the circulation and can be detected in acute stage blood samples
NS1
Ddx
Dengue like dses Viral respi and influenza-like dses Early stages of malaria Mild yellow fever Scrub thypus Viral hepatitis Leptospirosis
Lab findings (5)
1 pancytopenia (after 3-4d) 2 neutropenia <2,000/uL 3 platelets rarely fall below 100,000/uL 4 normal ranges Venous clotting BT and PTT Plasma fibrinogen 5 TT positive
Lab findings that may occur during primary dengue (4)
Mild acidosis
Hemoconcentration
Inc transaminase
Hypoproteinemia
ECG
1 sinus bradycardia
2 ectopic ventricular foci
3 flattened T waves
4 prolongation of PR interval
Mc hg abnormalities during DHF and DSS
Hemoconcentration Inc in HCt >20% Thrombocytopenia Prolong BT Mod dec Prothrombin level
Other lab abnormalities
-moderate elevations of serum transaminase levels
-consumption of complement
-mild metabolic acidosis with hyponatremia,
occasionally hypochloremia, slight elevation of serum urea nitrogen, and hypoalbuminemia
Roentgenograms of the chest reveal in nearly all patients with dengue shock syndrome
pleural effusions (right >left)
Can be used to detect serosal effusions of the thorax or abdomen
Ultrasonography
Characteristic signs of increased vascular permeability
Thickening of the gallbladder wall and the presence of perivesicular fluid
Treatment
Supportive
- Bed rest - febrile period
- Antipyretics < 40°C
- Analgesics or mild sedation - pain
- Fluid and electrolyte replacement
2 drugs C/I and should not be used because of their effects on hemostasis/blood clotting
Aspirin
Salicylates
A medical emergency that may occur in any child
who lives in or has a recent travel history to a tropical destination
Dengue shock syndrome
Management of dengue hemorrhagic fever and dengue shock syndrome includes
1 evaluation of
VS
hemoconcentration
dehydration
electrolyte imbalance
2 close monitoring for 48 hr
3 O2 for cyanotic patients
4 Rapid IV replacement of fluids and electrolytes
5 Normal saline > Ringer lactated (shock)
6 Plasama/colloid preparations if ≤10 mmHg or when elevation of hct persists after replacement of fluids
7 Oral rehydration
Care must be taken to avoid this which may contribute to cardiac failure
Overhydration
May be required to control bleeding but should NOT be given DURING HEMOCONCENTRATION but only after evaluation of hg or hct values
Transfusions of fresh blood
may be required for children who are markedly agitated
Sedation
Complications. During the fluid reabsorptive phase, this may be life-threatening and is heralded by a decrease in hematocrit with wide pulse pressure
What are necessary to give/do during this situation?
Hypervolemia
Diuretics and digitalization
Most frequent complications in infants and young children of primary infections with dengue fever and dengue-like diseases
Fluid and electrolyte losses
hyperpyrexia
febrile convulsions
Uncommon complications but may occur at any
stage
Epistaxis
petechiae
purpuric lesions
May occur during a high temperature (complication)
Convulsions
Infrequently, after the febrile stage these complications may occur in children (4)
prolonged asthenia
mental depression
bradycardia
ventricular extrasystoles
Prevention
1 Dengue vaccines (Dengvaxia) - 9 above in highly endemic areas
2 Avoiding daytime mosquito bites
-insecticides
-repellents
-body covering with clothing
-screening of houses
-destruction of A. aegypti breeding sites
3 tight-fitting lid or thin layer of oil
4 larvicide
5 ultra-low-volume spray equipment (adulticide malathion)
4S laban sa
Search and destroy breeding sites
Self protection measures
Seek early consultation
Say no to indiscriminate fogging
