Dengue Fever Virus

Indications for Testing

Flu-like illness with exanthem in endemic area or in patient with appropriate travel history

Criteria for Diagnosis

WHO case definition for dengue fever

Case Definition for Dengue Fever

Probable case

Acute febrile illness with headache, retro-orbital pain, myalgia, arthralgia, rash, hemorrhagic manifestations, leucopenia plus one of the following two conditions
- Supportive serology test results, including
  - Reciprocal hemagglutination-inhibition antibody titer ≥1,280
  - Comparable IgG ELISA titer
  - Positive IgM antibody test on a late-acute or convalescent-phase serum specimen
- Occurrence at the same location and time as other confirmed cases of dengue fever

Confirmed case

Laboratory criteria
- Isolation of DV from serum or autopsy samples
- Demonstration of a ≥fourfold change in reciprocal IgG or IgM antibody titers to ≥1 DV antigens in paired serum samples
- Demonstration of DV antigen in autopsy tissue, serum, or CSF samples by immunohistochemistry, immunofluorescence, or ELISA
- Detection of DV genomic sequences in autopsy tissue serum or CSF samples by PCR

WHO case definition for dengue hemorrhagic fever

Case Definition for Dengue Hemorrhagic Fever
The following criteria must all be present Fever (or history of acute fever) lasting 2-7 days (occasionally biphasic) Hemorrhagic tendencies (positive tourniquet test^*; petechiae; ecchymoses or purpura; bleeding from the mucosa, gastrointestinal tract, injection sites, or other locations; hematemesis or melena) Thrombocytopenia (≤100,000×10⁶ cells/L)^† Evidence of plasma leakage caused by increased vascular permeability and manifested by at least one of the following Rise in the packed cell volume ≥20% above average for age, sex, and population Drop of ≥20% in packed cell volume after volume replacement treatment Signs of plasma leakage (eg, pleural effusion, ascites, hypoproteinemia)
*Performed by inflating a blood pressure cuff on the upper arm to a point midway between the systolic and diastolic pressures for 5 minutes. Considered positive when ≥20 petechiae per 2.5 cm² are observed. May be negative or mildly positive during profound shock. Result is usually positive (sometimes strongly positive) if the test is conducted after recovery from shock. †This value represents a direct count using a phase-contrast microscope (normal is 200,000-500,000×10⁶/L). For outpatients, an approximate count from a peripheral blood smear is acceptable. In patients with normal values, 4-10 platelets per oil-immersion field (100 × the average of the readings from 10 oil-immersion fields is recommended) indicates an adequate platelet count. An average of ≤3 platelets per oil-immersion field is considered low (ie, <100,000×10⁶/L).

Case Definition for Dengue Hemorrhagic Fever

The following criteria must all be present

Fever (or history of acute fever) lasting 2-7 days (occasionally biphasic)
Hemorrhagic tendencies (positive tourniquet test^*; petechiae; ecchymoses or purpura; bleeding from the mucosa, gastrointestinal tract, injection sites, or other locations; hematemesis or melena)
Thrombocytopenia (≤100,000×10⁶ cells/L)^†
Evidence of plasma leakage caused by increased vascular permeability and manifested by at least one of the following
- Rise in the packed cell volume ≥20% above average for age, sex, and population
- Drop of ≥20% in packed cell volume after volume replacement treatment
- Signs of plasma leakage (eg, pleural effusion, ascites, hypoproteinemia)

*Performed by inflating a blood pressure cuff on the upper arm to a point midway between the systolic and diastolic pressures for 5 minutes. Considered positive when ≥20 petechiae per 2.5 cm² are observed. May be negative or mildly positive during profound shock. Result is usually positive (sometimes strongly positive) if the test is conducted after recovery from shock.

†This value represents a direct count using a phase-contrast microscope (normal is 200,000-500,000×10⁶/L). For outpatients, an approximate count from a peripheral blood smear is acceptable. In patients with normal values, 4-10 platelets per oil-immersion field (100 × the average of the readings from 10 oil-immersion fields is recommended) indicates an adequate platelet count. An average of ≤3 platelets per oil-immersion field is considered low (ie, <100,000×10⁶/L).

WHO case definition for dengue shock syndrome

Case Definition for Dengue Shock Syndrome
All criteria for DHF must be present, plus one of the following evidences of circulatory failure Rapid and weak pulse and narrow pulse pressure (<20 mm Hg [2.7 kPa]) Hypotension for age; cold, clammy skin; restlessness

Case Definition for Dengue Shock Syndrome

All criteria for DHF must be present, plus one of the following evidences of circulatory failure

Rapid and weak pulse and narrow pulse pressure (<20 mm Hg [2.7 kPa])
Hypotension for age; cold, clammy skin; restlessness

Laboratory Testing

Nonspecific laboratory tests
- CBC – frequently demonstrates leukopenia, thrombocytopenia, hemoconcentration
- Serum transaminases – may be elevated
- Serum electrolytes – hyponatremia not uncommon
Specific testing for laboratory diagnosis based on case-definition criteria
- Dengue-specific antibodies – reciprocal IgG or IgM antibodies by ELISA in paired serum samples
  - IgM reaches peak at 6 days – not useful in critical stage of diagnosis
- PCR – detect viral genomic sequences in autopsy tissue, serum, or CSF samples
- Cell culture for DV requires specialized mosquito cell lines not routinely available in the clinical laboratory setting

Histology

Demonstration of DV antigen in autopsy tissue by immunohistochemistry or immunofluorescence or in serum samples

Differential Diagnosis

Encephalitis/meningitis
- Flavivirus
  - Yellow fever
  - Japanese encephalitis
  - Arbovirus – West Nile virus, eastern equine encephalitis, western equine encephalitis
Other viruses
- Epstein-Barr virus
- Cytomegalovirus
- Measles virus
- Rubella virus
- HIV (initial infection)
- Lymphocytic choriomeningitis
Bacteria
Parasites
Sepsis
Acute viral hepatitis
- Hepatitis A, B, or C

Dengue fever is the most prevalent mosquito-borne viral disease in humans.

Epidemiology

Incidence – 50-100 million cases worldwide annually
- ~22,000 deaths associated with the disease (WHO estimate)
Transmission
- Dengue virus (DV) is transmitted by mosquito vectors
  - Aedes aegypti – subtropical and tropical locations worldwide
  - Aedes albopictus – Asia; also prevalent in southeastern U.S.
- Infection with any strain results in lifelong homologous immunity
- Dengue fever epidemics are common in tropical and subtropical areas worldwide
- Transplacental transmission possible

Organism

Dengue fever is caused by 1 of 4 DV serotypes (dengue 1-4)
- Single-stranded RNA virus of the Flaviviridae family surrounded by an icosahedral nucleocapsid
Cross reactions between members of Flaviviridae are common (eg, Banzi virus; Japanese, St. Louis, and Murray Valley encephalitis viruses; Rocio virus; West Nile virus, yellow fever virus)
Infection with any strain results in lifelong homologous immunity
Reinfection with a heterologous serotype of DV enhances the infection, resulting in the most severe clinical manifestations
- Dengue hemorrhagic fever (DHF)
- Dengue shock syndrome (DSS)

Clinical Presentation

Incubation – 4-7 days
Constitutional symptoms
- Fever typically lasts 5-7 days
- Headache and retro-orbital pain
- Arthralgia, myalgia
  - Severe myalgias ("breakbone fever")
- Prostration (incubation period of 2-6 days)
Rash
- Typically involves flushing erythema of the face, neck and chest during first 24-48 hours of symptoms
- Petechial, diffuse erythematous or morbilliform (occurs in 50-80% of patients)
  - Noted with “islands of sparing” (white skin in the middle of red skin)
Hemorrhagic manifestations – epistaxis, petechiae, gum bleeding
Hematologic – leukopenia, thrombocytopenia
Lymphadenopathy
DHF/DSS
- Majority of cases found in patients with recurrent dengue fever or who are reinfected with a different DV serotype
- In infants, most often occurs from primary DV infection when the mother has previous immunity
  - Majority of cases occur in children <15 years
  - Death occurs primarily in children between 5 – 15 years

Treatment

No vaccine available; treatment is supportive

Tests generally appear in the order most useful for common clinical situations

Test name: CBC with Platelet Count & Automated Differential

ARUP #: 0040003

Methodology: Automated Cell Count with Flow Cell Differential

Use:

Initial non-specific testing

Leukopenia, thrombocytopenia, hemoconcentration consistent with dengue virus

Test name: Aspartate Aminotransferase, Serum or Plasma

ARUP #: 0020007

Methodology: Quantitative Enzymatic

Use:

Initial non-specific testing

Elevated levels indicate the presence of acute hepatitis

Test name: Electrolyte Panel

ARUP #: 0020410

Methodology: Quantitative Ion-Selective Electrode/Enzymatic

Use:

Initial non-specific testing

Hyponatremia consistent with dengue virus

Test name: Dengue Fever Virus Antibodies, IgG & IgM

ARUP #: 0093096

Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Use:

Identify dengue virus as infectious agent in hemorrhagic febrile illness

Limitations: Usually requires paired convalescent samples

Follow-up: For equivocal results, repeat testing in 10-14 days

Additional Tests Available

Test name: Dengue Fever Virus Antibody, IgG

ARUP #: 0093097

Methodology: Semi-Quantitative Enzyme-Linked Immunosorbent Assay

Comments:

Test name: Dengue Fever Virus Antibody, IgM

ARUP #: 0093098

Methodology: Semi Quantitative Enzyme-Linked Immunosorbent Assay

Comments:

Best evidence for current infection is significant change on two appropriately timed specimens where both tests are done in the same laboratory at the same time

General

Delgado, Julio C., MD, MS. Medical Director, Protein Immunology at ARUP Laboratories; Associate Director, Histocompatibility and Immunogenetics Laboratory and Assistant Professor of Pathology, University of Utah

Comprehensive Review: July 2011
Last Update: July 2011

Encephalitis, Infectious

Leptospira Species

Lymphocytic Choriomeningitis

Meningitis, Acute

Plasmodium Species

Rickettsia rickettsii