Introduction
Dengue virus, is a single-stranded RNA virus belonging to the Flavivirus genus of the Falvivridae family. It exists as four antigenically distinct serotypes (Dengue 1-4)
Dengue virus is transmitted to an individual by serveral species of Aedes mosquitoes.
Dengue virus is endemic in more than 100 countires in tropical and subtropical regions of the world. Southeast Asia, including Cambodia, is an area of dengue hyperendemicity where the 4 serotypes are circulating simulatneously and the DHF cases are reported each year. An estimated 50-100 million Dengue infections and 250K-500K DHF/DSS with 1-30% mortality occur annually. It is difficult to control due to urbanization, overpopulation, increasing travel and failure to maintain effective control programs against mosquito vectors.
During 2023-2024, the median age of pateints with dengue, the percentage of patients hospitalized, and the pevalences of serotypes 2 and 3 increased compared with the previous decade. (“Epidemilogy of Dengue –Puerto Rico, 010-2024” December 12, 2024, 73(49); 1112-1117).
In the United States, dengue is generally an imported disease. The incubation period of 3-14 days (usually 3-7) generally provides that travel to an endemic area be involved (e.g., fever in travelers returned from Asia is associated with a 13-fold increased risk of dengue and a lower risk of malaria).
Clinical Manifestations
Mosquito-mediated (Aedes spp.) infection with the single-stranded RNA virus of 4 serotypes can be divided into 4 grades from very mild to severe and fatal when dengue hemorrhagic shock (DHF, grades III and IV) ensues. DHF generally follows reinfection with a different serotype. Infection with any one of the 4 serotypes produces classic Dengue fever, an illness with mild febrile symptoms. In fection by more than one serotype increases the risk of developing lethal Dengue hemorrahgic fever/shock syndrom (DHF/DSS) caused by vast hemorrhage and capillary plasma leakage.
After an incubation period of 2 to 7 days, the typical patient experiences the sudden onset of fever, headache, retroorbital pain, and back pain. There is often a macular rash on the first day which is centripetal (mainly in the center of the body) and is characterized by desquamation. There may also be adenopathy, palatal vesicles, and scleral injection. The illness may last a week, with additional symptoms usually including anorexia, nausea or vomiting, marked cutaneous hypersensitivity, and — near the time of defervescence — a maculopapular rash beginning on the trunk and spreading to the extremities and the face. Epistaxis and scattered petechiae are often noted in uncomplicated dengue, and preexisting gastrointestinal lesions may bleed during the acute illness.
Transmission: Symptoms
Dengue is a mosquitoborne viral illness that can caseu acute febrile illness, evere disease or death. Worldwide, the nubmer of dengue cases is increasing. During the alst dengue outbreak in Puerto Rico, for exampe, throughout 2010-2013, dengue virus (DENV) serotype 1 (DENV-1) predominated and the largest properotion of cases occurred among adolescents adn young adults aged 10-19. During 2023-2024, the mdian age of dengue cases increased to 26 years. After more than 10 years of DENV-1 predominance, the propotions of DENV serotypes 2 (DENV-2) and 3 (DENV-3) increased significantly during 2023-2024, with DENV-3 replacing DENV-1 as the prdominant serotype in Puerto Rico. “Epidemilogy of Dengue –Puerto Rico, 010-2024” December 12, 2024, 73(49); 1112-1117).
Detection of Dengue
IgM capture, and IgG EIAs, the serological methods of choice, are positive at 5-6 and 7-10 days after infection.1 High titers of specific IgG are characteristic of secondary infection. Cross-reactivities with JEV continue to plague some assays. Rapid tests of reasonable performance are available for the field.
Well-defined RT-PCR methods are now available for detection of DEN-1-DEN-4;viral variants relevant to PCR procedures, of which over 10 have been described, are important. Description of real-time RT-PCRs for viral hemorrhagic fevers is an admirable tour-de-force.
Detection of Dengue virus currently relies upon virus isolation or serological tests and typically requires days to weeks to complete. In addition, the immunological assays are compromised by cross-reactivity with other flaviviruses.
Molecular based diagnostic assays such as RT-PCR can provide quick and reliable results within a few hours.
No Dengue vaccine has been licensed yet.