1. Internal Medicine Workshop Series Laos September /October 2009
Dengue Fever
Internal Medicine Workshop Series Laos
September /October 2009

2. Many similarities and differences between dengue and leptospirosis
Write down
The difference in how infection occurs
2 history points that are the same and 2 that are different
2 physical examination points that are the same and 2 that are different
2 laboratory findings that are the same and two that are different

3. Dengue infection Most common arboviral illness worldwide
Caused by 1 of the 4 dengue viruses
DENV-1, DENV-2, DENV-3, DENV-4
Transmitted to humans by the bite of an infected mosquito
Genus Aedes
Day biting mosquito

4. Dengue virus transmission
Epidemic dengue
Single virus strain
High infection rates of 25-50%
Hyperendemic dengue
Continuous circulation of multiple viral serotypes
Hosts (humans) and vector (mosquito) are constantly present
Most adults are immune
Increases risk for dengue hemorrhagic fever

5. Dengue Initial dengue infection may be… Recurrent infection
Asymptomatic
Nonspecific febrile illness
Dengue fever symptom complex (DF)
Recurrent infection
Person previously infected by one serotype
May develop dengue hemorrhagic fever (DHF)
Bleeding and endothelial leak
If severe….Dengue shock syndrome (DSS)

6. Clinical: history Chills, fever (as high as 41 degrees )
Starts on day 3
Lasts 5-7 days
Stops when viremia ends
May come and go in children
Headache, severe, behind eyes
Nausea, vomiting
Maculopapular rash (starts on day 3, stays for 2-3 days)
Face, thorax, flexor surface

7. Clinical: history Myalgias Arthralgias Hemorrhage Abdominal pain
Low back, arms, legs
Arthralgias
Knees and shoulders
Hemorrhage
Bleeding from nose, gums
Melena, menorrhagia, hematemesis
Abdominal pain
Fatigue and malaise
Conjunctival injection, sore throat, cough

8. Clinical: physical Fever Rash (1/2 patients), petechiae, purpura
Conjunctiva injection (1/3 patients DHF)
Pharyngeal injection (97% pts with DHF)
Lymphadenopathy
Hepatomegaly (DHF)

9. Clinical: physical Hemorrhagic complications Cardiac Evidence of shock
Petechiae and bleeding at venipuncture site
Nasal or gingival bleeding, melena, hematemesis, menorrhagia
Cardiac
Tachycardia with fever
Myocarditis can cause bradycardia and conduction defect
Evidence of shock
Hypotension
Prolonged capillary refill
Weak rapid pulse
Cool mottled skin
Decreased urine output

10. Tourniquet test
Inflate a blood pressure cuff on the upper arm to midway between diastolic and systolic blood pressure
Hold for 5 minutes
Positive test if more than 20 petechiae per square inch on arm

11. Laboratory Lymphocytosis Leukopenia, lymphopenia
before fever ends, and with shock
Leukopenia, lymphopenia
end of febrile illness
Hemoconcentration and high hematocrit
Thrombocytopenia
50% of cases of DF
DHF and DSS plts < 100
Hyponatremia, metabolic acidosis, elevated BUN, mildly increased ALT, AST
Prolonged PT (INR), PTT, low fibrinogen

12. Laboratory Isolation of dengue virus from blood
4 X increase in immunoglobulin antibody titers from paired serum
Virus antigen in tissue
Polymerase chain reaction (PCR) demonstrating virus in tissue, serum or CSF

13. Diagnosis: dengue fever
Acute febrile illness of 2-7 days duration with 2 or more of the following
Severe headache
Retro-orbital pain
Severe myalgias
Arthralgias
Characteristic rash
Hemorrhagic complications
Leukopenia
Lab diagnosis as above
SUSPECTED CASE: fits clinical description
PROBABLE CASE: fits clinical description and 1) serology supports or 2) other confirmed cases of dengue in location
CONFIRMED CASE : fits clinical description and confirmed by laboratory

14. Diagnosis: dengue hemorrhagic fever (DHF)
Probable or confirmed case of dengue fever AND hemorrhagic tendancies
Positive tourniquet test
Petechiae, ecchymoses, purpura
Bleeding from mucosa, GI tract, injection sites, etc
Thrombocytopenia
Evidence of plasma leakage from vascular permeability
20% rise in hematocrit
20% drop in hematocrit after volume replacement
Pleural effusion, ascites, hypoproteinemia

15. Diagnosis: dengue hemorrhagic shock (DHS)
Case meets all above criteria AND evidence of circulatory failure
Rapid weak pulse
Hypotension
Cool clammy skin
Altered mental status

16. Differential diagnosis
Malaria
Leptospirosis
Viral hepatitis
Meningococcemia
Typhus
Yellow fever
Meningitis
Influenza
Septic shock (bacterial)

17. Treatment Usually self limited illness Supportive care Acetominophen
No aspirin, NSAIDs or corticosteroids
IV fluids
Ringer lactate
Dextran 40, albumin, starch
Fresh frozen plasma (if coagulopathy)

18. Prevention Avoid being bitten by the mosquito
Wear DEET containing mosquito repellent
Wear protective clothing
Try to remain in well-screened or air conditioned places
Use indoor mosquito repellent sprays
Eliminate the breeding ground of mosquitoes
No stagnant water