Author: Hadia Zafar
Introduction
Infectious diseases (ID) are characterized disorders caused by an agent, often a type of microorganism, that can impair a person's health. These diseases are considered to be an increased threat to global health security. A contributing factor to this threat is the increase in emerging and re-emerging infectious diseases. An analysis of the basic understanding, significance, and drivers of dengue and Lyme disease will be done. This analysis will aid in the comprehension of the similarities and differences between the two diseases.
Basics of Dengue and Lyme Disease
Both dengue and Lyme disease are emerging or re-emerging vector-borne diseases, but the vectors by which they spread are different. The vector by which dengue is spread is through either the Aedes aegypti or Aedes albopictus mosquito. The dengue virus (DENV), the causative agent for dengue fever, is a single-stranded enveloped RNA virus. In understanding the disease, it is important to note how the disease is spread. A mosquito is infected by a human who already has the dengue virus. After the mosquito is infected, it spreads the disease to other humans by biting during the day.
Lyme disease, on the other hand, is caused by an interaction with a black-legged tick infected with Borrelia burgdorferi, Borrelia mayonii, Borrelia afzelii, or Borrelia garini. Although the morbidity rate of Lyme disease is low, the quality of life of someone who has chronic Lyme disease is significantly reduced.
Significance of Dengue and Lyme Disease
Understanding the dengue vaccine’s unique delivery limitations, the potential for Lyme disease’s antibiotic resistance, and the One Health perspective were key factors in selecting these emerging and re-emerging diseases.
Dengue Vaccine
A major concern for vaccine delivery for dengue is an individual’s potential to get severe dengue. An individual who has not had a previous dengue infection cannot receive the vaccine. Vaccination can put previously uninfected individuals at greater risk for severe dengue through antibody-dependent enhancement. This emphasizes the importance of testing before vaccine delivery, which can be difficult during an outbreak.
Antibiotic Resistance
The prolonged use of antibiotics for Lyme disease as treatment is controversial but has shown benefits in some cases. Because of this prolonged use, the potential for antibiotic resistance should be considered. Currently, resistance is not a source of concern, but it can be in the future. Therefore, better treatment options should be explored.
One Health Perspective
The application of One Health is important for the understanding of emerging and re-emerging infectious diseases. This perspective recognizes the integral connections among humans, animals, and the environment in relation to health and promotes interdisciplinary collaborations to tackle public health issues.
Two models that are included in this approach are the infectious disease triangle and the zoonotic disease triangle. The infectious disease triangle is a conceptual model that displays the interactions between the host, agent, and the environment about infectious disease spread. The zoonotic disease triangle analyzes the interconnectivity between a host amplifier, reservoir host, vector, and human host. These models allow for exploring and analyzing various drivers of emergence for both dengue and Lyme Disease.
Drivers of Dengue
Climate change has become a growing concern for public health. Due to increased greenhouse gas emissions, there has been an increase in the earth's atmospheric temperature. This increase has led to the expansion of dengue's geographic distribution, thus making climate change a major driver of this disease.
Another major driver of dengue is urbanization. As human populations move towards urban centers, there is also an increase in the development of slum cities. The sanitation of these cities is low due to a lack of resources. A key public health concern is standing water in these areas because these are breeding grounds for mosquito-borne diseases. The prevalence of dengue in this area would be a concern due to the high population density. Although dengue is not transmitted human-to-human, an area with low sanitation, poverty, and high population density would suffer greatly if a dengue outbreak occurred.
Drivers of Lyme Disease
The greatest driver of Lyme disease is human behavior. Common activities, such as hiking in a wooded area, camping, and hunting, can exponentially increase your risk of infection. Simple actions like wearing permethrin threading cloths, using better insect repellents like nootkatone, and becoming educated on the prevalence of the disease in the local area can significantly decrease infection risk.
The other major driver of Lyme disease is the changes in land use resulting from infrastructure development. When a non-developed area becomes developed, the risk for humans in the area of contracting Lyme disease increases because of the increased interaction with vectors of disease. Consultation with public health officials during the construction phase of new developments could significantly decrease this risk.
Similarities and Differences between Dengue and Lyme Disease Epidemiology
Dengue is contracted by a mosquito-borne disease-carrying DENV 1, DENV 2, DENV 3, or DENV 4. It is estimated that 390 million people worldwide have been infected with dengue. There is a notable increase in the number of dengue cases in the summer. Approximately 25,000 people die each year due to severe dengue progression.
Lyme disease is caused by interaction with a black-legged tick infected with Borrelia burgdorferi and, rarely, Borrelia mayonii. 476,000 people are estimated to be infected with Lyme in North America. The case incidence is higher in the spring and summer months. This disease occurs most often in young children and older adults. The mortality rate is relatively low, but the quality of life of an infected individual who develops chronic Lyme varies but can be severely impacted.
Global Distribution
The global distribution of dengue has shifted vastly over the past century, expanding in geographic areas affected. Dengue was initially observed in south and southeast Asia, but due to the disease's drivers, the distribution has spread. Dengue is now observed in every continent except Antarctica. The threat of a dengue outbreak is no longer concentrated in primarily Asia and Africa. There is now a threat of an outbreak anywhere around the world.
Unlike dengue, Lyme disease diagnosis is primarily concentrated in the United States (U.S.), Canada, and Europe. In the U.S., disease incidence is concentrated in the Northeast, mid-Atlantic, and upper Midwest regions.
Disease Burden
The most significant disease burden is the economic burden of both dengue and Lyme diseases. An analysis of Lyme disease's economic burden revealed a significant economic impact of 786 million USD. The economic burden of dengue is greater than the burden for Lyme disease. The estimated burden of dengue in the U.S. between 2002 and 2007 was 2.1 billion USD.
There is a constant threat of emerging and re-emerging diseases. This threat is enhanced by the pressure put forth by the drivers of disease. Disease surveillance will enhance the understanding of the epidemiology, drivers, and distribution of diseases. This understanding will facilitate policymaking and scientific exploration that has the potential to control disease emergence.
Conclusion
To decrease the biosecurity threat associated with emerging and re-emerging diseases, the comprehension of the drivers of disease is vital. This understanding was facilitated by the One Health perspective, which can be used for the potential treatment of dengue and Lyme disease.
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