Dengue fever presents a significant public health challenge in Sri Lanka. The warm, humid climate and increasing urbanization contribute to its prevalence, making dengue an endemic disease across all 26 districts and affecting individuals of all age groups. An estimated average annual incidence of 175 cases per 100,000 population highlights this mosquito-borne illness.
Understanding Dengue Transmission
Dengue is transmitted primarily through the bite of infected female Aedes aegypti and Aedes albopictus mosquitoes. These mosquitoes are highly anthropophilic, meaning they prefer to bite humans, and are active during daylight hours, with peak biting intensity occurring about two hours after sunrise and before sunset.
These mosquitoes lay their eggs in clean, stagnant water, which makes various common household and public containers potential breeding sites. Discarded items such as plastic containers, glassware, tins, and tires, along with water storage barrels, cement tanks, and even natural formations like leaf axils and tree holes, can serve as nurseries for mosquito larvae. The eggs can survive in dry conditions for up to a year and hatch when exposed to water. In Sri Lanka, particularly during monsoon seasons, the accumulation of water in such sites contributes to increased mosquito populations and, consequently, higher rates of dengue transmission.
The transmission cycle involves a human-mosquito-human pathway. An infected mosquito bites a human, transmitting the dengue virus. This infected person, who may or may not show symptoms, can then be a source of the virus for uninfected mosquitoes for about 4 to 5 days, and up to 12 days, after the onset of their first symptoms. A single infected Aedes mosquito can bite multiple people, potentially leading to several dengue cases in the same area.
Recognizing Dengue Symptoms
Dengue fever typically begins with a sudden onset of high fever, often reaching 104°F (40°C), accompanied by a severe headache. Individuals frequently experience pain behind the eyes, which may worsen with eye movement, along with significant muscle and joint pain, leading to the informal name “breakbone fever”. Other common symptoms include nausea, vomiting, a skin rash, and swollen glands.
While many cases are mild, a small proportion can progress to severe dengue. Warning signs indicating the potential progression to severe dengue typically appear on or after the third day of fever, sometimes as the fever starts to subside. These signs include:
Severe abdominal pain or tenderness
Persistent vomiting
Mucosal bleeding (such as from the mouth, nose, or gums)
Lethargy or restlessness
Liver enlargement greater than 2 cm
Laboratory findings, such as a rising hematocrit (a 20% increase from baseline) concurrent with a rapid decrease in platelet count, also indicate severe dengue.
Prevention and Control Efforts
Preventing dengue involves a combination of personal protective measures and community-wide initiatives focused on eliminating mosquito breeding sites. Individuals can reduce their risk of mosquito bites by using insect repellents on exposed skin and wearing clothing that covers most of the body, such as long-sleeved shirts and long pants. Using mosquito nets and ensuring homes have intact window and door screens can also provide protection.
At the household level, a primary strategy is the regular elimination of stagnant water sources where mosquitoes can lay eggs. This includes emptying and scrubbing clean water storage tanks, flower pots, vases, and fridge trays at least once a week. Proper disposal of discarded items like bottles, tins, and tires is also important, as these can collect rainwater and become breeding grounds. Regular cleaning and proper waste management are crucial to prevent the accumulation of water in and around residential premises and public places.
Broader public health initiatives complement individual efforts. The National Dengue Control Unit (NDCU), established under the Ministry of Health, leads technical guidance for social mobilization and coordinates integrated vector management. This involves community clean-up campaigns, public awareness programs disseminated through electronic and print media, and targeted interventions in high-risk areas. While adulticide spraying (fogging) and larvicides were used in the past, a more proactive integrated vector management approach, emphasizing source reduction campaigns with multisector partnership, is gaining momentum. Enhanced real-time surveillance for early warning allows for preparedness and a coordinated response to potential outbreaks.
Managing Dengue Infection
There is no specific antiviral treatment for dengue fever; management focuses on supportive care to alleviate symptoms and prevent complications. Rest is highly recommended for patients, along with maintaining adequate hydration. Patients should be encouraged to drink plenty of fluids, including oral rehydration solutions, fruit juice, water, or traditional options like king coconut water. For fever control, only paracetamol should be used, and nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen or diclofenac, as well as aspirin, should be strictly avoided due to their anticoagulant properties, which can increase the risk of bleeding. Tepid sponging can also help reduce fever in between paracetamol doses.
Close monitoring for warning signs of severe dengue is crucial, especially as fever begins to subside, typically around days 3 to 7 of the illness. Patients or their caregivers should be alert for symptoms and seek immediate medical attention if these occur. Healthcare facilities in Sri Lanka are equipped to manage dengue cases, with national guidelines focusing on early detection of plasma leakage and prompt treatment of shock. Daily monitoring of platelet count and hematocrit levels from the third day of illness is often performed to assess the progression of the disease and guide medical decisions.