- Dengue is a viral infection transmitted by *Aedes*
mosquitoes, common in tropical and subtropical regions.
- Symptoms likely include high fever, severe headache,
joint/muscle pain, rash, and mild bleeding, appearing 4–10 days after a bite.
- Severe dengue (dengue hemorrhagic fever) can cause
life-threatening complications like bleeding or organ failure.
- Evidence suggests no specific antiviral treatment exists;
supportive care (hydration, pain relief) is key.
- Prevention focuses on mosquito control and vaccines like
Dengvaxia, used in high-risk areas.
*Overview -
Dengue is a mosquito-borne viral disease caused by four
dengue virus serotypes (DENV-1 to DENV-4), spread primarily by *Aedes aegypti*
and *Aedes albopictus* mosquitoes. It’s a major public health issue in over 100
countries, particularly in Asia, the Pacific, the Americas, Africa, and the
Caribbean, with an estimated 100–400 million infections annually. While most
cases are mild or asymptomatic, severe dengue can be fatal, especially in
children in endemic areas.
*Symptoms -
Symptoms typically begin 4–10 days after an infected mosquito
bite and last 2–7 days. Common signs include:
- High fever (up to 104°F/40°C)
- Severe headache
- Pain behind the eyes
- Joint and muscle pain ("breakbone fever")
- Rash (often appearing 2–5 days after fever onset)
- Mild bleeding (e.g., nosebleeds, gum bleeding, or easy
bruising)
- Fatigue, nausea, and vomiting
Severe dengue, affecting about 1 in 20 symptomatic cases, may
develop 24–48 hours after fever subsides, with warning signs like:
- Severe abdominal pain
- Persistent vomiting
- Rapid breathing
- Bleeding gums or nose
- Fatigue/restlessness
- Blood in vomit/stool
- Pale, cold, or clammy skin
Severe cases can lead to dengue hemorrhagic fever or dengue
shock syndrome, causing plasma leakage, severe bleeding, or organ failure,
requiring urgent medical care.
*Treatment -
There’s no specific antiviral treatment for dengue.
Management focuses on supportive care:
- **Mild Cases**: Rest, ample hydration
(water, oral rehydration solutions), and fever/pain relief with acetaminophen
(paracetamol). Avoid NSAIDs like ibuprofen or aspirin due to bleeding risks.
- **Severe Cases**: Hospitalization for
intravenous fluids, blood transfusions (if bleeding occurs), and monitoring for
complications like shock or organ impairment.
Early recognition of warning signs and access to medical care
significantly reduce mortality, with severe dengue fatality rates below 1% with
proper treatment but up to 20% without.
*Prevention -
Prevention centers on avoiding mosquito bites and reducing
mosquito populations:
- **Personal Protection**: Use
mosquito repellents (DEET, picaridin), wear long-sleeved clothing, and use
insecticide-treated bed nets, especially during dawn and dusk when *Aedes*
mosquitoes are active.
- **Environmental Control**: Eliminate
standing water in containers, buckets, or tires to prevent mosquito breeding.
Use larvicides or introduce fish that eat mosquito larvae in water storage.
- **Community Measures**: Fogging
with insecticides during outbreaks and public health campaigns to clear
breeding sites.
**Vaccines**:
- **Dengvaxia** (CYD-TDV), the first dengue vaccine, is
licensed in several countries for ages 9–45 in high-risk areas. It’s most
effective in those previously infected with dengue, reducing severe outcomes by
about 80% in seropositive individuals. However, it may increase severe dengue
risk in seronegative people, so it’s used selectively.
- Other vaccines, like TAK-003 (Qdenga) and TV003/TV005, are
in development or limited use, showing promise for broader protection.
The WHO recommends integrated vector management and
vaccination in endemic areas with high transmission.
*Global Impact and Outlook -
Dengue cases have surged eightfold since 2000, driven by
urbanization, climate change, and global travel, with 5.2 million cases
reported in 2019, particularly in the Americas. Asia bears 70% of the global
burden, with countries like India, Indonesia, and the Philippines heavily
affected. Climate factors, like warmer temperatures and heavy rainfall, expand
mosquito habitats, increasing outbreak risks.
Complications include severe bleeding, organ damage, or death
in severe cases, particularly in second infections with a different serotype
due to antibody-dependent enhancement (ADE). Immunity to one serotype doesn’t
protect against others and may worsen subsequent infections.
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*Detailed Report on Dengue -
*Definition and Epidemiology -
Dengue is a viral illness transmitted by *Aedes* mosquitoes,
caused by four antigenically distinct dengue virus serotypes (DENV-1 to
DENV-4), belonging to the *Flaviviridae* family. It ranges from asymptomatic or
mild flu-like illness to severe forms like dengue hemorrhagic fever (DHF) or
dengue shock syndrome (DSS). The WHO estimates 390 million annual infections,
with 96 million symptomatic cases, and a 3.9 billion population at risk across
129 countries. Historically a tropical disease, dengue is now reported in
Europe and the U.S. due to climate-driven mosquito spread.
*Transmission -
Dengue spreads through bites from infected female *Aedes
aegypti* (primary vector) or *Aedes albopictus* mosquitoes, which thrive in
urban areas and bite during the day. Mosquitoes become infected by biting an
infected human during the viremic phase (4–5 days after symptom onset) and can
transmit the virus after an 8–12-day incubation period. Rarely, dengue spreads
via blood transfusions, organ transplants, or from mother to fetus. Infected
humans, including asymptomatic cases, are the main reservoir, amplifying urban
outbreaks.
*Risk Factors -
- Living in or traveling to tropical/subtropical regions
(e.g., Southeast Asia, Latin America, Caribbean)
- Urban or peri-urban settings with poor sanitation and water
storage
- Previous dengue infection (increases severe dengue risk due
to ADE)
- Children and older adults in endemic areas
- Climate factors like high temperatures and rainfall
*Diagnosis -
Diagnosis relies on clinical evaluation and lab tests:
- **Clinical**: Based on fever plus symptoms like
rash, pain, or bleeding, with travel history to endemic areas.
- **Lab Tests**:
-
**RT-PCR**: Detects viral RNA in blood during the first 5–7 days (gold
standard).
- **NS1
Antigen Test**: Rapid test for early detection (days 1–7).
- **IgM/IgG
ELISA**: Detects antibodies; IgM rises after 5–7 days, IgG indicates past
infection.
- **Complete Blood Count**: Low platelet count and
hemoconcentration in severe cases.
Differentiating dengue from similar illnesses (e.g.,
chikungunya, Zika, malaria) is critical, as symptoms overlap.
*Treatment Details -
No antiviral drugs target dengue, so treatment is
symptomatic:
- **Outpatient Care (Mild Cases)**: Oral
rehydration (electrolyte solutions), acetaminophen for fever/pain, and rest.
Patients should avoid dehydration and monitor for warning signs (e.g., severe
abdominal pain, persistent vomiting).
- **Hospital Care (Severe Cases)**: IV fluids
to correct plasma leakage, blood transfusions for significant bleeding, and
oxygen or ventilatory support for shock or organ failure. Monitoring includes
hematocrit, platelet counts, and vital signs.
The WHO’s 2009 classification divides dengue into dengue
without warning signs, dengue with warning signs, and severe dengue, guiding
treatment escalation.
*Prevention Strategies -
Effective prevention combines vector control, personal
protection, and vaccination:
- **Vector Control**:
- **Source
Reduction**: Remove standing water from containers, flowerpots, or gutters
weekly.
-
**Chemical Control**: Use larvicides (e.g., temephos) in water containers
and adulticides (e.g., pyrethroids) during outbreaks.
-
**Biological Control**: Introduce *Wolbachia*-infected mosquitoes, which
reduce dengue transmission, or larvivorous fish.
- **Personal Measures**: Insect
repellents, protective clothing, and mosquito nets. Indoor residual spraying
and vaporizers enhance protection.
- **Vaccination**: Dengvaxia is WHO-recommended
for seropositive individuals in endemic areas, requiring pre-vaccination
screening. New vaccines like TAK-003 show broader efficacy and are under review
in some regions.
Community engagement, urban planning, and climate adaptation
(e.g., drought-resistant water storage) are critical for sustainable control.
*Complications and Prognosis -
Most dengue cases resolve within a week, but severe dengue
can cause:
- **Plasma Leakage**: Leads to
hypovolemic shock (DSS) with low blood pressure and organ failure.
- **Severe Bleeding**: Due to low
platelets or vascular damage (DHF).
- **Organ Impairment**: Rare but
includes liver, heart, or neurological complications.
Mortality is low (<1%) with timely care but higher in
resource-poor settings. Second infections with a different serotype increase
severe dengue risk due to ADE, where non-neutralizing antibodies enhance viral
entry into cells.
*Global Efforts and Challenges -
The WHO’s Global Strategy for Dengue Prevention and Control
(2012–2020) aimed to reduce mortality by 50% and morbidity by 25%, with ongoing
efforts under the Neglected Tropical Diseases roadmap. Challenges include:
- Urbanization and population growth fueling mosquito
breeding.
- Climate change expanding *Aedes* ranges (e.g., southern
Europe, U.S.).
- Limited vaccine access and complex serotype dynamics.
- Misdiagnosis in areas with overlapping diseases like Zika
or chikungunya.
Recent advances, like *Wolbachia* programs in Indonesia and
Brazil, show up to 77% reduction in dengue incidence, offering hope for
scalable solutions
*Summary -
Dengue is a widespread viral disease with significant global
impact, driven by *Aedes* mosquitoes and exacerbated by urbanization and
climate change. It ranges from mild fever to life-threatening severe dengue,
managed through supportive care due to the lack of specific antivirals. Prevention
relies on mosquito control, personal protection, and targeted vaccination.
Early diagnosis and access to care are critical to reducing mortality, with
ongoing research into better vaccines and vector control offering future
promise.
