Unraveling the Mystery of Dengue Fever and How to Stay Safe by Dr. Tania Peter Jang, Kemena Pacific Hospital
Dengue is a viral infection caused by the flavivirus, transmitted to humans through the bite of infected mosquitoes. There are four serotypes of the dengue virus: DENV-1, DENV-2, DENV-3, and DENV-4. According to the World Health Organization (WHO), the global incidence of dengue has risen dramatically in recent decades, particularly in tropical and subtropical regions. In 2023, a historic high of over 6.5 million cases and more than 7,300 dengue-related deaths were reported across 80 countries, including many in Asia. The highest recorded cases in Asia in 2023 were from Bangladesh (321,000), Malaysia (111,400), Thailand (150,000), and Vietnam (369,000).
Several factors contribute to the increasing spread of dengue, including the changing distribution of vectors, climate change, and extreme weather conditions such as the El Niño phenomenon in 2023. Additionally, fragile healthcare systems—particularly in the wake of the COVID-19 pandemic—have also played a role in the spread of the disease.
Symptoms and Severe Dengue Risk
Many dengue cases are asymptomatic, mild, or misdiagnosed as other febrile illnesses, leading to potential underreporting. According to the U.S. Centers for Disease Control and Prevention (CDC), only 1 in 4 people infected with dengue will develop symptoms. Those who do may experience flu-like symptoms, including:
- Fever
- Pain behind the eyes
- Muscle, joint, or bone pain (hence the nickname “break-bone fever”)
- Nausea and vomiting
- Skin rash
Symptoms typically last between 2 to 7 days, with most individuals recovering in about a week. However, in some cases, the disease can progress rapidly to severe dengue (dengue hemorrhagic fever), which is a life-threatening emergency. Approximately 1 in 20 symptomatic cases may develop severe dengue, with warning signs such as:
- Severe abdominal pain
- Frequent vomiting
- Lethargy or restlessness
- Bleeding symptoms (e.g., vomiting blood, blood in stools, nosebleeds, or bleeding gums)
Clinicians also monitor for signs such as fluid accumulation, liver enlargement, and progressive increases in hematocrit. If infected, it is crucial to get adequate rest, stay hydrated, take paracetamol for pain, and monitor for severe symptoms. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin should be avoided.
Transmission and Risk Factors
Dengue is primarily transmitted through the bite of infected female Aedes aegypti and Aedes albopictus mosquitoes. These mosquitoes become carriers of the virus after biting an infected individual and subsequently spread the virus to other humans. The Aedes species also transmit Zika and chikungunya viruses. They typically breed in water-filled containers such as buckets, flowerpots, and vases and are active both indoors and outdoors during the day and night.
Pregnant women infected with dengue can pass the virus to their fetus, potentially causing complications such as fetal death, low birth weight, and premature birth. While the dengue virus has been detected in breast milk, the benefits of breastfeeding outweigh the risks, and mothers are encouraged to continue nursing even if they have dengue.
Prevention Measures
The most effective way to prevent dengue is to avoid mosquito bites. WHO and CDC recommend the following preventive measures:
- Physical barriers: Use window and door screens, or keep them closed.
- Protective clothing: Wear long pants, shoes, socks, and long-sleeved shirts, preferably treated with permethrin.
- Avoid peak mosquito activity: Limit outdoor activities at dawn and dusk when mosquitoes are most active.
- Use mosquito repellents: Apply EPA-registered repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus (OLE), para-menthane-diol (PMD), or 2-undecanone. Pregnant and breastfeeding women can use these repellents safely when following the instructions. However, OLE and PMD should not be used on children under 3 years old.
- Stay in protected environments: Choose accommodations with air conditioning and window/door screens while traveling.
- Use mosquito nets: If resting during the day, use insecticide-treated nets.
Mosquito Breeding Prevention
Preventing mosquito breeding is essential to controlling dengue. Effective measures include:
- Proper disposal of solid waste and removing artificial water-holding containers (e.g., tires, buckets, pools, trash containers)
- Weekly cleaning, emptying, and covering of domestic water storage containers
- Using appropriate insecticides in outdoor water storage areas
Protecting Babies and Children
To protect young children from mosquito bites:
- Dress them in clothing that covers their arms and legs
- Use mosquito netting over strollers and baby carriers
Dengue Vaccination
The CDC emphasizes that dengue vaccines can provide long-term protection against all four dengue serotypes, reducing the risk of severe disease and hospitalization. Currently, two dengue vaccines are available:
- Dengvaxia (Sanofi Pasteur) – Available in the U.S. since 2022 for individuals aged 9 to 45 or 9 to 60 (depending on country regulations) with a confirmed past dengue infection. A pre-vaccination screening test is required, as vaccinating dengue-naïve individuals increases their risk of severe disease if infected post-vaccination.
- Qdenga (Takeda) – The first dengue vaccine approved and available in Malaysia, suitable for individuals aged 4 and above, regardless of prior dengue infection. It is administered in two doses, three months apart. Clinical trials show the vaccine’s efficacy begins one month after the second dose. However, its long-term protection duration remains unclear.
Common side effects of Qdenga include mild-to-moderate pain at the injection site, headache, muscle pain, malaise, and fever, typically lasting 1 to 3 days. The vaccine is contraindicated in:
- Pregnant or breastfeeding women
- Individuals with hypersensitivity to vaccine components
- People with symptomatic or asymptomatic HIV infection with compromised immune function
- Those on immunosuppressive therapies (e.g., chemotherapy, high-dose corticosteroids)
Dengue Vaccine for Travelers
Will travelers benefit from dengue vaccination? Frequent travelers, long-term expatriates, and migrants are more likely to have had past dengue infections (seropositive) and may benefit more from vaccination than first-time or short-term travelers, who are less likely to have prior exposure (seronegative). Therefore, the vaccine’s benefits may vary depending on an individual’s travel history and risk level.
Conclusion
Dengue fever remains a growing global health threat, with increasing incidence due to climate change and expanding mosquito habitats. While preventive measures, early symptom recognition, and proper medical care are crucial in controlling the disease, vaccination provides an additional layer of protection. Staying informed and taking proactive steps can help individuals and communities stay safe from dengue.
