Dengue fever is an acute infectious disease caused by the dengue virus, involving complex biological, environmental, and social factors. The virus is primarily transmitted through bites of infected mosquito vectors (Aedes aegypti and Aedes albopictus), and the severity of the disease is closely related to the viral strain, host immune status, and environmental conditions. Understanding these causes helps in formulating effective prevention strategies and public health measures.
The transmission cycle of dengue involves three core components: virus-carrying mosquitoes, human hosts, and environmental conditions. The circulation of the virus between mosquitoes and humans depends on factors such as mosquito density, population density, and climate change. Although genetic factors are not the primary risk, individual differences in immune response to the virus may lead to varying disease severity. The following sections explore these key causes from different perspectives.
While genetic factors are not direct transmission routes for dengue, individual genetic differences do influence disease manifestation after infection. Studies show that specific human leukocyte antigen (HLA) genotypes may increase the risk of severe disease, such as HLA-B*13:02 and its association with hemorrhagic dengue. Additionally, innate immune-related genes (e.g., Toll-like receptor polymorphisms) may impair the host’s initial recognition of the virus.
Family history in certain populations may reflect a combination of genetic predisposition and environmental exposure. For example, some Asian populations have evolved certain resistance mechanisms due to long-term exposure in endemic areas, but this does not completely eliminate infection risk. It is important to note that genetic factors generally have a smaller impact on disease severity compared to environmental and behavioral factors; therefore, public health efforts primarily focus on environmental control.
Climate conditions are critical environmental factors influencing mosquito breeding. An increase of 1°C in temperature can shorten the mosquito life cycle by 2-3 days, while relative humidity above 60% significantly enhances mosquito survival. Urbanization creates breeding sites such as water containers (discarded tires, rainwater tanks), especially in peri-urban areas, forming “urban hotspots.” For example, during the rainy season in subtropical cities, mosquito density can surge 3-5 times, directly elevating infection risk.
Urban planning and infrastructure also play crucial roles. Communities lacking proper drainage systems have mosquito densities 4-7 times higher than modern cities. Poorly managed irrigation systems in agriculture, such as rice paddies and irrigation ditches, can become large breeding grounds, especially in Asian rice-growing regions.
Human daily behaviors directly impact infection risk. Populations not using protective measures (such as bed nets and repellents) have infection rates 2-3 times higher than those with routine protection. In tropical regions, outdoor activities during peak mosquito activity times (early morning and dusk) increase the likelihood of infection. Poor household hygiene, such as failing to eliminate water containers around the home, directly increases mosquito breeding opportunities.
Population mobility is also a key behavioral factor. International travelers can introduce the virus into non-endemic areas, potentially triggering outbreaks if local mosquito vectors are present. Occupational movement (e.g., agricultural workers in forests) may also increase exposure. Additionally, socioeconomic disparities between urban and rural areas lead to poorer sanitation in low-income communities, which often have infection rates 2-4 times higher than surrounding areas.
Repeated infection with different serotypes of the dengue virus, known as antibody-dependent enhancement, is a critical factor in severe disease. When a person is infected a second time with a different serotype, the immune response may produce incomplete neutralizing antibodies, facilitating viral entry into macrophages and increasing the risk of hemorrhagic symptoms. This immunological mechanism explains why communities with high reinfection rates tend to have higher proportions of severe cases.
Regions with limited healthcare resources face higher risks of complications. Lack of prompt diagnosis and supportive treatment can lead to metabolic disturbances or uncontrolled bleeding. Co-infections with other viruses (such as Zika) may exacerbate symptoms, although such cases are relatively rare.
Urbanization and land use changes are emerging risk factors. Large-scale infrastructure projects (such as road construction that disrupts natural ecosystems) may destroy habitats of natural predators, indirectly increasing mosquito populations. Urban heat island effects raise local temperatures, prolonging the transmission season. These factors must be considered in environmental management strategies.
The causes of dengue fever are the result of multifactorial interactions: viral genetic characteristics determine transmission potential, environmental conditions control mosquito density, human behaviors influence exposure opportunities, and immune response variability affects disease severity. Only through integrated prevention strategies—including environmental sanitation, community education, and real-time monitoring—can the global burden of this disease be effectively reduced.
The dengue vector mosquitoes (Aedes aegypti and Aedes albopictus) breed faster in warm, humid environments. Water containers such as flower vases and discarded items are more likely to hold water during rainy seasons. Elevated temperatures also increase mosquito activity, biting frequency, and shorten the virus transmission cycle, making outbreaks more common under specific climatic conditions.
Why do some people have mild symptoms while others develop severe dengue after infection?The severity of symptoms is related to individual immunity, the viral serotype, and prior exposure to different serotypes. If a person has been infected with one serotype before, subsequent infection with a different serotype may cause more severe disease due to antibody-dependent enhancement. Older adults, those with underlying health conditions, or immune deficiencies are more prone to severe manifestations such as hemorrhagic shock.
Why should I avoid using aspirin or other NSAIDs to reduce fever in dengue?NSAIDs can worsen dengue-associated coagulopathy, increasing the risk of internal bleeding. It is recommended to use acetaminophen (paracetamol) for fever reduction and to monitor for signs of bleeding or thrombocytopenia. Patients should follow medical advice and avoid self-medicating.
Is the dengue vaccine suitable for all age groups? Can it completely prevent infection?The currently approved dengue vaccine (Tamarix) in Taiwan is recommended only for individuals aged 9-45 who have previously been infected. Those who have not been infected should undergo blood testing to confirm prior infection, as vaccination in seronegative individuals may increase severe disease risk. The vaccine offers approximately 60-90% protection but does not provide complete immunity; protective measures against mosquito bites are still necessary.
How can I prevent household transmission when a family member has dengue?During the febrile period, the patient should use mosquito nets to prevent bites. Since the vector mosquitoes are active during the day, indoor mosquito control measures such as electric mosquito repellents and mosquito traps should be used. Thoroughly eliminate water containers around the home. Close contacts should also take protective measures, and if symptoms like fever or headache occur, seek medical attention promptly and inform healthcare providers about contact history for early diagnosis.
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