Dengue virus is an arbovirus transmitted by mosquitoes which causes significant morbidity and mortality among children in tropical regions, especially in resource limited countries. The objective of this protocol is to compare the sensitivity and specificity of clinical gestalt and two rapid antigen tests for dengue virus and to compare the gene expression of leukocytes in distinct dengue fever disease phenotypes module-based RNA microarray technology.

This is a biology protocol with no treatment regimen associated. Blood collection will be drawn from subjects in El Salvador to be tested in an effort to improve detection and test sensitivity and specificity of a dengue NS1 Ag ELISA, dengue NS1 Ag STRIP, and clinical suspicion for the detection of dengue virus infection in children in San Salvador, El Salvador compared to the gold standard, PCR. This protocol will also seek to identify and compare gene transcription patterns characteristics of each dengue virus disease phenotype in children.

Inclusion Criteria Part A:

• Age: Greater than or equal to 6 months and less than 13 years
• One of the following; History of fever OR a history of spontaneous or provoked bleeding

Inclusion Criteria Part B:

• Gender: Female
• Age: greater than or equal to 36 months
• Tanner stage less than 2
• One of the following criteria: Classical Dengue Fever, Dengue Hemorrhagic Fever or Dengue Shock Syndrome

Exclusion Criteria for both parts:

• Obvious alternative explanation for the actual illness
• Cellulitis/Abscess
• Osteomyelitis
• Varicella
• Urinary Tract Infection
• Known immunocompromising condition

Children subject presenting to Benjamin Bloom Children's Hospital in San Salvador, El Salvador.