DENGUE FEVER

Question 1

Organism Type

Answer 1

single-stranded RNA viruses of the genus Flavivirus

Question 2

Scientific name:

Answer 2

denguevirus (DENV)

Question 3

Subtypes:

Answer 3

DENV-1, DENV-2, DENV-3, DENV-4 serotypes, is

possible to be infected four times.

Question 4

Common Name(s):

Answer 4

‘breakbone fever’ & ‘dandy fever’

Question 5

Prevalence:

Answer 5

endemic in tropics & subtropics & >100 countries
worldwide + Puerto Rico, Virgin Islands, US-affiliated Pacific Islands.
Outbreaks occurred in FL/HI/TX.

Question 6

Predisposing Factors:

Answer 6

Urban environments, outdoor activities during

spring & summer; mosquito bites

Question 7

Transmitted Via:

Answer 7

Aedes aegypti mosquito; blood transfusion/organ

donation; M2C

Question 8

Vector

Answer 8

Yes

Question 9

Dengue Fever Follows 3 phases

Answer 9

(a) Febrile
(b) Critical
(c) Convalescent

Question 10

(1) Typically lasts 2–7 days and can be biphasic.
(2) Signs and symptoms may include severe headache; retroorbital pain;
muscle, joint, and bone pain; & macular or maculopapular rash.
(3) Minor hemorrhagic manifestations, including petechiae, ecchymosis,
purpura, epistaxis, bleeding gums, hematuria, or a positive tourniquet
test result.

Answer 10

Febrile Stage

Question 11

(1) Critical phase of dengue begins at defervescence and typically lasts
24–48 hours.
(2) Most patients clinically improve during this phase and move on to
recovery & convalescence stage.
(a) Thus, these patients really don’t have a critical phase, per se,
and go from febrile stage to recovery stage.
(3) However, those with substantial plasma leakage develop severe
dengue as a result of a marked increase in vascular permeability.

Answer 11

Mild DF – Critical Stage

Question 12

(1) As plasma leakage subsides, patient enters convalescent phase.
(2) Pt begins to reabsorb extravasated intravenous fluids, pleural, &
abdominal effusions.
(3) As a patient continues to improve, hemodynamic status stabilizes and
diuresis ensues.
(4) The patient’s hematocrit stabilizes or may fall because of the dilutional
effect of the reabsorbed fluid, and the white cell count usually starts to
rise, followed by a recovery of platelet count.
(5) The convalescent-phase rash may desquamate and be pruritic

Answer 12

Mild DF – Recovery Stage

Question 13

(1) Initially, physiologic compensatory mechanisms maintain adequate
circulation, which narrows pulse pressure as diastolic blood pressure
increases.
(2) Patients with severe plasma leakage will have pleural effusions or
ascites, hypoproteinemia, and hemoconcentration.
(a) These patients may appear well despite early signs of shock.
(3) However, once hypotension develops, systolic blood pressure rapidly
declines, and irreversible shock and death may ensue despite
resuscitation efforts.
(a) Known as ‘Dengue Shock Syndrome’
(4) Patients can also develop severe hemorrhagic manifestations,
including:
(a) Hematemesis, bloody stool, melena, menorrhagia, especially
in prolonged shock.

Answer 13

Severe DF – Critical Stage

Question 14

(1) a relatively accurate way
to get a general determination a patients’ capillary fragility or
hemorrhagic tendency.
(2) Fairly effective ‘no frills’ test that used to further justify a presumptive
Dengue DX without the ability or access to confirmatory laboratory
testing.

Answer 14

Tourniquet Test

Question 15

Two of the hallmarks of severe Dengue are

Answer 15

Infection-induced
capillary permeability (leaky capillaries) and
disordered/diminished blood clotting.

Question 16

Two of the hallmarks of severe Dengue are infection-induced
capillary permeability (leaky capillaries) and
disordered/diminished blood clotting. Medical science
believes this happens for 3 main reasons:

Answer 16

1) Leaky capillaries (in the critical phase) occurring 2/2 to
an immune system response to the virus.
2) Dengue-infected cells become necrotic, and then affect
both coagulation (blood clotting) and fibrinolysis
(breakdown of clots)
3) Low platelet count, which causes degrades the normal
clotting response.

Question 17

Tourniquet Test Steps:

Answer 17

(a) Obtain baseline BP & annotate the readings. Then, let the arm
a rest for 90-120 seconds.
(b) Attach BP cuff, and inflate to a point midway between the
Systolic & Diastolic pressures obtained at baseline.
1) Example: Baseline BP was 120/80; cuff will be inflated
to 100 mmHg
(c) Keep inflated cuff on arm for 5 minutes, then deflate & wait
2 min.(d) Count petechiae below AC fossa.
(e) A positive test is 10 or more petechiae per 1 square inch.

Question 18

Diagnosis

Answer 18

(1) Clinicians should consider dengue in a patient who was in an endemic
area within 2 weeks of symptom onset.
(a) Laboratory confirmation can be made from a single acutephase serum specimen obtained early (≤7 days after fever
onset)
(b) Later in the illness (≥4 days after fever onset), IgM against
dengue virus can be detected with ELISA.

Question 19

Treatment
Mild DF
Severe DF

Answer 19

(2) Mild DF:
(a) Patients stay well hydrated and avoid aspirin, aspirincontaining drugs, and NSAIDS because of their anticoagulant
properties.
(b) Invasive medical procedures such as NG intubation,
intramuscular injections and arterial punctures are avoided
due to bleeding risk
(c) Fever should be controlled with acetaminophen (Max 4g in
24 hrs.)
(d) Febrile patients should avoid mosquito bites to reduce risk of
further transmission.
(3) Severe DF:
(a) Typically requires ICU-level monitoring & blood products.
(b) Maintenance of the patient’s body fluid volume is critical to
severe dengue care.

Question 20

Prevention

Answer 20

(1) No prophylaxis is available to prevent dengue.
(2) Risk increases with duration of travel and disease incidence in the
travel destination (such as during the rainy season and during
epidemics).
(3) Travelers going to areas with risk of dengue should take steps to avoid
mosquito bites.

Question 21

Disposition

Answer 21

(1) Med Advice and/or MEDEVAC
(2) Patients presenting with S/S of even mild dengue should be evacuated
to definitive medical care facility as soon as possible.