Dengue fever is a mosquito-borne viral infection caused by the dengue virus. It is transmitted to humans through the bite of infected Aedes mosquitoes, commonly known as tiger mosquitoes. Dengue is frequently found in tropical countries and outbreaks commonly occur during the rainy season each year. Symptoms can range from mild illness to severe, life-threatening complications if not diagnosed and treated promptly.
How Dengue Fever Spreads?
Dengue fever is caused by four different serotypes of the dengue virus: DENV-1, DENV-2, DENV-3, and DENV-4. Female Aedes mosquitoes, which are most active during the daytime, serve as the primary carriers of the virus.
When a mosquito bites a person infected with dengue during the fever stage, the virus enters the mosquito’s body and multiplies in its digestive system. After an incubation period of approximately 8–12 days inside the mosquito, the virus travels to the mosquito’s salivary glands. Once the infected mosquito bites another person, the virus enters the bloodstream and may cause infection. Symptoms usually appear within 3–15 days after being bitten.
Who Is at Risk of Severe Dengue Fever?
Dengue fever can affect people of all ages and genders, but it is more commonly found among school-age children and young working adults. Individuals at higher risk of severe symptoms or complications include:
- Infants and older adults
- People with obesity
- Pregnant women
- Individuals with blood disorders or abnormal hemoglobin conditions
- Patients with congenital heart disease
- Individuals with chronic illnesses such as:
- Diabetes
- Hypertension
- Asthma
- Ischemic heart disease
- Kidney failure
- Chronic liver disease
- People taking steroid medications or Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
Symptoms of Dengue Fever
For a first dengue infection, approximately 80–90% of patients experience mild symptoms or no symptoms at all. Common symptoms may include:
- High fever
- Headache
- Muscle and joint pain
- Bone pain
- Skin rash
However, a second dengue infection caused by a different serotype may lead to severe dengue fever, which can become life-threatening. Dengue illness is generally divided into three phases:
1. Febrile Phase
During this stage, patients experience a high fever almost continuously, typically ranging from 38.5°C to 40–41°C. The fever may not respond well to fever-reducing medications.
Other symptoms may include:
- Loss of appetite
- Nausea and vomiting
- Abdominal pain
- Skin rash or small bleeding spots on the body, arms, or legs
***This phase usually lasts 2–7 days.***
2. Critical Phase
The critical phase usually begins when the fever starts to subside.
Patients Without Complications : Symptoms gradually improve and recovery begins.
Patients with Severe Dengue: Some patients may develop complications such as:
- Low platelet count, leading to easy bleeding
- Persistent nausea, vomiting, abdominal pain, and fatigue
- Circulatory failure or shock due to plasma leakage into the lungs or abdominal cavity
Approximately one-third of severe dengue patients may experience shock (hypovolemic shock), which often occurs when the fever suddenly drops. Shock can develop between the 3rd and 8th day of illness.
Warning signs include:
- Restlessness
- Cold hands and feet
- Rapid weak pulse
- Blood pressure changes
Severe bleeding may also occur due to low platelet levels, including:
- Nosebleeds
- Vomiting blood
- Black stools (melena)
This critical phase usually lasts 24–48 hours. If fever persists for more than 2 days or symptoms worsen, immediate medical attention is recommended.
3. Recovery Phase
During recovery, patients gradually improve. Common signs of recovery include:
- Improved appetite
- Stabilized blood pressure
- Stronger and slower pulse
- Increased urination
- Mild skin rash or small red spots on the body
Diagnosis of Dengue Fever
Anyone with suspected dengue symptoms should seek medical care at a hospital or clinic as early as possible.
Doctors may perform blood tests to detect:
- Dengue virus
- Dengue antibodies
- Red blood cell concentration (hematocrit)
- White blood cell count
- Platelet count
Follow-up blood tests may be required to monitor platelet levels and blood concentration. A decreasing platelet count together with increasing hematocrit levels may indicate plasma leakage, which can lead to shock and may require intravenous fluid replacement.
How to Prevent Dengue Fever
1. Avoid Mosquito Bites
- Sleep under mosquito nets
- Wear long-sleeved shirts and long pants
- Use mosquito repellents, especially products containing DEET
2. Eliminate Mosquito Breeding Sites
- Cover water storage containers tightly with lids, mesh, or cloth
- Change standing water daily in small containers such as flower vases
- Add sand to plant saucers to absorb excess water
- Dispose of unused containers, bottles, cans, and old tires that can collect water
Dengue vaccination is another important preventive measure. Currently, dengue vaccines can help reduce the risk of dengue infection and severe disease in adults and children over 4 years of age.
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