Dengue fever is a viral illness transmitted to humans primarily through infected Aedes aegypti and Aedes albopictus mosquitoes. It is a global health concern, particularly in tropical and subtropical regions. The disease is caused by the dengue virus (DENV), which exists as different types, known as serotypes. DENV-2 is one such serotype.
The Four Dengue Serotypes and DENV-2’s Role
The dengue virus has four distinct serotypes: DENV-1, DENV-2, DENV-3, and DENV-4. Infection with one serotype provides lifelong immunity to it, but only temporary and partial protection against the others. This cross-protection typically lasts for several months to a few years.
DENV-2 is frequently associated with severe dengue outbreaks globally. It is known to cause more serious forms of dengue, including severe dengue or dengue shock syndrome. In endemic areas, DENV-2 infection rates often rise, leading to large outbreaks.
Recognizing Dengue Symptoms
Dengue fever typically manifests 4 to 10 days after a mosquito bite. The illness progresses through three phases: febrile, critical, and recovery. The febrile phase begins with a sudden high fever, often 39 to 40 degrees Celsius, and usually lasts 2 to 7 days.
During the febrile phase, common symptoms include severe headache, pain behind the eyes, muscle and joint pains, and a rash. Nausea, vomiting, and mild bleeding like easy bruising or nosebleeds can also occur. Most patients improve and move directly into the recovery phase.
The critical phase usually occurs between days 3 and 7, often as fever decreases. This phase typically lasts 1 to 2 days and requires close monitoring for severe complications. The recovery phase follows, usually spanning 2 to 3 days, as symptoms gradually improve and vital signs normalize.
Why DENV-2 Can Be More Dangerous
A secondary infection with a different dengue serotype, especially DENV-2 after a prior infection, significantly increases the risk of severe dengue. This heightened risk is largely attributed to antibody-dependent enhancement (ADE). During ADE, pre-existing antibodies from a previous infection, instead of neutralizing the new serotype, help the virus enter and replicate more efficiently within immune cells. This can lead to increased viral replication and an exaggerated immune response, contributing to severe disease.
Severe dengue, which can manifest as dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), is a life-threatening condition characterized by vascular leakage, bleeding, and hypotensive shock. Warning signs typically appear 24 to 48 hours after the fever subsides. These include severe abdominal pain, persistent vomiting, bleeding from the gums or nose, and blood in vomit or stool.
Additional warning signs include fluid accumulation in the chest or abdomen, rapid breathing, lethargy, restlessness, and an enlarged liver. A progressive increase in hematocrit, indicating blood thickening from fluid leakage, is also a sign. Prompt medical attention is important if any of these warning signs are observed, as early supportive therapy can reduce the risk of death.
Diagnosis, Treatment, and Prevention
Dengue, including DENV-2, is diagnosed using various blood tests. These include the NS1 antigen test, which detects a viral protein early in infection, and polymerase chain reaction (PCR) tests that identify viral genetic material. Serological tests, which look for antibodies (IgM and IgG), are also used.
There is no specific antiviral treatment for dengue. Management primarily involves supportive care to alleviate symptoms and prevent complications. This includes maintaining hydration, managing pain with acetaminophen (avoiding NSAIDs like ibuprofen due to bleeding risks), and monitoring for warning signs of severe dengue.
Prevention strategies focus on controlling mosquito populations and personal protection. Eliminating mosquito breeding sites, such as standing water, is effective. Using insect repellents, wearing long-sleeved clothing, and ensuring screens on windows and doors also reduce mosquito bites. A dengue vaccine, Dengvaxia, is available in some regions for individuals aged 9 to 16 with a confirmed history of prior dengue infection. This recommendation is due to the increased risk of severe disease in those who have not had a prior infection, linked to ADE.