Introduction
Dengue virus (DENV) is a positive-sense, single-stranded RNA (ssRNA) virus classified within the genus Orthoflavivirus of the Flaviviridae family. It exists as four antigenically distinct serotypes (Dengue 1-4). The genus includes over 70 medically important flaviviruses, many of which are known to cause human disease. These viruses predominantly affect regions in the tropics and subtropics, where approximately 3.9 billion people reside, making dengue a major global health concern.
DENV is the etiological agent of dengue fever, an acute febrile illness historically referred to as “break-bone fever” due to its associated myalgia. Transmission occurs predominantly via the bite of female Aedes mosquitoes, primarily Aedes aegypti, although Aedes albopictus can also transmit the virus in rare instances. See Wang
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 cause acute febrile illness, severe disease or death. Worldwide, the number of dengue cases is increasing. During the last dengue outbreak in Puerto Rico, for example, throughout 2010-2013, dengue virus (DENV) serotype 1 (DENV-1) predominated and the largest proportion of cases occurred among adolescents adn young adults aged 10-19. During 2023-2024, the median age of dengue cases increased to 26 years. After more than 10 years of DENV-1 predominance, the proportions 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).
Pathology:
Antibody-dependent enhancement (ADE). DENV exploits host antibodies to enhance viral entry and replication, a process known as antibody-dependent enhancement (ADE). Instead of neutralizing the virus, DENV-specific antibodies can facilitate viral uptake via Fcγ receptors, increasing infection severity. Neutralizing antibodies play a key role in infection control by
blocking viral attachment and preventing membrane fusion. Most of these antibodies target the envelope (E) protein, which carries major DENV antigenic epitopes. However, pre-existing antibodies from a prior infection may fail to neutralize a different DENV serotype, instead promoting Fc receptor-mediated viral entry, leading to ADE.
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.
Antigen Detection: Nonstructural protein 1 (NS1) antigen plays a significant role in DENV replication within host cells. It is produced and released into the bloodstream of infected individuals and is considered an essential biomarker for early detection of flavivirus infections. NS1 detection assays—including enzyme-linked immunosorbent assays (ELISA) and rapid diagnostic tests (RDTs)—enable identification of acute-phase infections. Currently, there is one U.S. FDA-approved NS1
test, the DENV Detect NS1 ELISA (InBios International), which provides qualitative results. Beyond this, numerous other commercially available NS1 antigen detection kits are employed. These encompass both ELISA-based and rapid diagnostic tests (RDTs), specifically: DENV Detect NS1 ELISA and Dengue NS1 Detect Rapid Test (InBios International); Platelia Dengue NS1 Ag ELISA and Dengue NS1 Ag STRIP (BioRad, France); Panbio Dengue Early ELISA (2nd generation) and Panbio Dengue Early Rapid (Alere, USA); and the SD Bioline Dengue NS1 Ag Rapid Test (Abbott, USA).
Although NS1 antigen detection has become a widely used tool for early dengue diagnosis, particularly during the acute febrile phase, it presents several important limitations that affect its overall diagnostic performance. One major concern is its reduced sensitivity in secondary dengue infections. In such cases, pre-existing dengue antibodies rapidly form immune complexes with the circulating NS1 antigen, thereby masking it from detection by standard assays. Another limitation lies in the short diagnostic window. NS1 antigen is typically detectable only within the first 5–7 days following symptom onset. After this period, NS1 levels decline rapidly, which can lead to false-negative results in patients who present later in the
course of illness. This narrow window restricts the utility of NS1 testing to early presenters and underscores the need for complementary diagnostic tools, especially in resource-limited settings.
Antibody detection is one of the most widely used methods for dengue diagnosis, particularly for supportive or retrospective confirmation of infection. The samples for serological tests are usually serum or plasma, however, alternative specimen types such as dried blood spots obtained from venous or capillary blood, saliva, and CSF have also been explored. Despite serological tests widespread used, serological diagnosis of DENV infection is significantly hampered by cross-reactivity issues, particularly between flavivirus envelope (E) proteins, which are the primary targets for most serological diagnosis.
IgM antibodies typically become detectable between days 6 and 8 post-symptom onset in primary DENV infection, though some patients may exhibit IgM as early as day 3. Peak IgM levels are generally observed around two weeks post-infection, with detectability lasting up to three months. However, IgM titers tend to be lower and decline more rapidly in secondary infections, and prior exposure to another flavivirus can further reduce IgM titers. n contrast, IgG antibodies develop around the fourteenth day of illness and persist for a lifetime, indicating past infection or
immunity. In secondary dengue infections, IgG levels rise rapidly within 1–2 days of symptom onset, often alongside IgM antibodies. The IgM/IgG ratio helps differentiate between primary and
secondary infections, with a higher ratio suggesting primary infection.
Treatment:
Dengue fever is generally a self-limiting disease; however, mortality rates can rise significantly in cases of severe dengue. Early detection of shock is critical, as patient outcomes largely depend on timely intervention. See Wang
If shock is identified early, indicated by a narrowing pulse pressure, and intravenous fluids are administered promptly, the prognosis is excellent. Most patients recover fully within 24–48 h without long-term complications. Conversely, the prognosis becomes poor in cases of prolonged shock, especially when blood pressure becomes unmeasurable. See Wang
Currently, there are no approved specific antiviral therapies for dengue, and clinical management remains primarily supportive. Treatment typically involves careful fluid replacement, analgesics for symptom relief, and adequate rest. See Wang
The lack of targeted antiviral options highlights the vital importance of prevention strategies.
Vaccination:
Several dengue vaccines have been developed and approved for specific populations. CYD-TDV (Dengvaxia®, Sanofi Pasteur) is licensed for individuals with confirmed prior dengue infection. TAK003 (QDENGA®, Takeda), a live-attenuated tetravalent vaccine, has demonstrated broad efficacy and received WHO prequalification in 2024. See Wang
Another promising candidate, the Butantan-DV vaccine, developed in Brazil using a similar live-attenuated platform, has completed late-phase clinical trials and shown favorable safety and
efficacy profiles. However, access to and implementation of these vaccines differ across countries, and their role should be regarded as adjunctive to—rather than a substitute for—comprehensive clinical management. Although advances in dengue vaccine development
represent significant progress in disease prevention, they do not eliminate the need for timely and effective clinical management. See Wang
Achieving robust, balanced protection against all four dengue serotypes remains challenging, and vaccine effectiveness can vary depending on factors such as age, immune status, and local
transmission dynamics. Thus, even with broader vaccine availability, supportive care remains essential to manage severe cases and prevent dengue-related mortality. See Wang