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

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

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

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

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)

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

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

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

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

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

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

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

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

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

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

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

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)

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