Dengue fever (DF) is an acute, self limiting, viral disease that is characterized by fever, headache, body pains, rash, lymphadenopathy, and prostration. In its most severe form, dengue hemorrhagic fever (DHF), infected patients will experience severe fever and renal failure leading to the often fatal dengue shock syndrome (DSS). There are 4 strains of dengue virus, each serologically distinct. Infection with 1 strain does not protect the host from infection by the others. DHF and DSS occur most commonly in individuals that have been infected previously by another strain. The presence of circulating, non-neutralizing, cross-reactive DV antibody may act as an immune infection enhancement factor. Both dengue virus-specific immunoglobulin G (IgG) and IgM antibodies are usually found in the sera from patients with acute primary infections, while the IgM response may be low or sometimes even absent in secondary dengue fever. Furthermore, a strong cross-reactivity exists among the flavivirus family. As a result, the antibody response may be difficult to interpret with regard to an acute dengue fever, if other flavivirus infections cannot be excluded by clinical, laboratory, or epidemiological means. More recently real-time RT-PCR methods have been developed to detect Dengue virus in the patients’ blood. The detection of dengue virus RNA by reverse transcriptase PCR (RT-PCR) in human blood samples is highly indicative of acute dengue fever. Dengue virus can be detected in the blood from patients for approximately the first 5 days of symptoms.