8.3 Emerging and Re-emerging Infectious Diseases
5 min read•july 31, 2024
Emerging and re-emerging infectious diseases pose significant challenges to global health. These diseases, caused by newly recognized or evolving pathogens, can spread rapidly and have far-reaching impacts on public health, economies, and societies worldwide.
Understanding the factors behind disease emergence is crucial. Environmental changes, human behavior, and microbial adaptation all play roles. Public health responses involve , global collaboration, and innovative research to detect, prevent, and control these infectious threats.
Emerging and Re-emerging Diseases
Definition and Characteristics
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- Emerging infectious diseases involve newly recognized or evolved pathogens causing public health concerns
- Re-emerging infectious diseases encompass previously known pathogens reappearing or increasing in incidence after decline
- Causative agents include bacteria, viruses, fungi, or parasites
- Pose challenges due to limited medical knowledge, lack of effective treatments, or rapid spread potential
- Classification remains dynamic, changing based on epidemiological patterns and scientific understanding
Types and Examples
- emerged late 20th century, becoming a global impacting health, economics, and social structures
- emerged in 2019, causing pandemic with widespread morbidity, mortality, and socioeconomic disruption
- , discovered 1947, emerged as significant global threat in 2015-2016
- disease, identified 1976, caused several African outbreaks, with 2014-2016 West African epidemic demonstrating widespread impact potential
- strains re-emerged, posing significant challenge to global health systems
- re-emerged and expanded geographic range due to urbanization and
- Influenza strains periodically re-emerge, exemplified by 2009 H1N1 pandemic
Factors for Disease Emergence
Environmental and Ecological Factors
- Ecological changes alter pathogen habitats and host-pathogen interactions
- Deforestation disrupts natural ecosystems
- Urbanization increases population density and alters living conditions
- Climate change affects vector distribution and pathogen survival
- and increased international travel facilitate rapid pathogen spread across borders
- Air travel allows diseases to cross continents within hours
- International trade contributes to the movement of vectors and pathogens
- Zoonotic spillover events enable pathogens to jump from animal hosts to humans
- Wet markets bringing diverse animal species into close contact with humans
- Encroachment on wildlife habitats increases human-animal interactions
Human Behavior and Societal Factors
- Changes in human behavior create new transmission routes for pathogens
- Sexual practices influence the spread of sexually transmitted infections
- Intravenous drug use contributes to the transmission of blood-borne pathogens
- Breakdown of public health measures leads to re-emergence of previously controlled diseases
- Declining vaccination rates result in resurgence of vaccine-preventable diseases
- Deteriorating sanitation infrastructure increases risk of waterborne illnesses
- Socioeconomic factors exacerbate spread and impact of infectious diseases
- Poverty limits access to healthcare and preventive measures
- Overcrowding in urban slums facilitates disease transmission
Microbial Adaptation and Evolution
- Microbial adaptation and evolution contribute to emergence of new strains
- Genetic mutations allow pathogens to evade host immune responses
- Horizontal gene transfer enables acquisition of virulence factors
- Development of antibiotic resistance poses significant challenge
- Overuse and misuse of antibiotics select for resistant bacterial strains
- Limited development of new antibiotics exacerbates the problem
Examples of Infectious Diseases
Viral Diseases
- HIV/AIDS emerged as global pandemic, impacting health, economics, and social structures
- Transmitted through bodily fluids, primarily affecting immune system
- Antiretroviral therapy has transformed HIV from fatal to chronic manageable condition
- SARS-CoV-2 caused COVID-19 pandemic, resulting in widespread morbidity and mortality
- Highly contagious respiratory virus spread through droplets and aerosols
- Rapid development of vaccines and antivirals showcased scientific advancements
- Zika virus emerged as significant threat, particularly to pregnant women
- Transmitted by Aedes mosquitoes and through sexual contact
- Caused microcephaly in newborns and Guillain-Barré syndrome in adults
Bacterial Diseases
- Multi-drug resistant tuberculosis strains pose significant challenge to global health
- Airborne bacterial infection primarily affecting lungs
- Extended treatment regimens and limited effective antibiotics complicate management
- Methicillin-resistant Staphylococcus aureus (MRSA) emerged as major healthcare concern
- Resistant to multiple antibiotics, complicating treatment of infections
- Community-acquired MRSA strains now prevalent outside healthcare settings
Vector-borne Diseases
- Dengue fever re-emerged and expanded geographic range due to environmental changes
- Transmitted by Aedes mosquitoes in tropical and subtropical regions
- Four distinct serotypes complicate vaccine development and immunity
- West Nile virus spread rapidly across North America since its introduction in 1999
- Transmitted by Culex mosquitoes, with birds serving as amplifying hosts
- Causes neuroinvasive disease in small percentage of infected individuals
Public Health Response to Outbreaks
Surveillance and Early Detection
- Surveillance systems crucial for early detection and monitoring of disease outbreaks
- Syndromic surveillance monitors patterns of symptoms in populations
- Molecular epidemiology uses genetic sequencing to track pathogen spread and evolution
- Rapid response teams and emergency preparedness plans essential for effective outbreak management
- Teams trained to quickly deploy to affected areas
- Plans outline roles, responsibilities, and procedures for various outbreak scenarios
Global Collaboration and Communication
- International collaboration and information sharing vital for coordinating global responses
- facilitates communication between countries
- Global Outbreak Alert and Response Network (GOARN) mobilizes resources for outbreaks
- Public health communication strategies employed to educate public and combat misinformation
- Clear, consistent messaging from health authorities
- Engagement with community leaders to promote trust and compliance
Research and Intervention Strategies
- Research and development efforts focus on creating new diagnostics, therapeutics, and vaccines
- Rapid diagnostic tests enable quick identification of pathogens
- Novel therapeutic approaches, including monoclonal antibodies and antivirals
- Vaccine platforms allowing for rapid development and adaptation to new pathogens
- Infection control measures implemented to contain disease spread
- Isolation of infected individuals to prevent transmission
- to identify and exposed individuals
- Implementation of personal protective equipment (PPE) protocols
- adopted to address interconnectedness of human, animal, and environmental health
- Collaborative efforts between human health, veterinary, and environmental sectors
- Holistic strategies targeting multiple aspects of disease emergence and spread
Key Terms to Review (23)
Antimicrobial resistance: Antimicrobial resistance (AMR) is the ability of microorganisms such as bacteria, viruses, fungi, and parasites to resist the effects of medications that once effectively treated them. This phenomenon poses significant challenges to public health by making infections harder to treat, leading to longer hospital stays, higher medical costs, and increased mortality. AMR is closely linked to the principles of infectious disease transmission, as resistant organisms can spread from person to person and through various environments, complicating efforts to control infections.
Centers for Disease Control and Prevention: The Centers for Disease Control and Prevention (CDC) is a national public health agency in the United States, responsible for protecting public health and safety by controlling and preventing disease, injury, and disability. The CDC plays a vital role in surveillance, research, health education, and policy development, ensuring communities are equipped to respond to health threats and improving overall population health.
Climate change: Climate change refers to significant alterations in global temperatures and weather patterns over time, primarily driven by human activities such as the burning of fossil fuels, deforestation, and industrial processes. These changes lead to extreme weather events, rising sea levels, and alterations in ecosystems, impacting public health through increased exposure to infectious diseases and new health challenges that societies must prepare for in the future.
Contact Tracing: Contact tracing is a public health strategy used to identify and notify individuals who have been in close contact with someone diagnosed with an infectious disease. This process helps to control outbreaks by ensuring that potentially infected individuals are informed, monitored, and provided with guidance to prevent further transmission. The effectiveness of contact tracing relies on timely identification of cases and cooperation among the community, which has significant implications in the management of infectious diseases and public health achievements.
Covid-19: COVID-19 is a highly contagious respiratory illness caused by the SARS-CoV-2 virus, first identified in December 2019 in Wuhan, China. This disease has had a profound impact on global health and highlighted the importance of vaccination and public health measures to control outbreaks. As a pandemic, COVID-19 brought attention to both vaccine-preventable diseases and the need for robust immunization programs, while also being an example of an emerging infectious disease that can rapidly spread and affect populations worldwide.
Dengue fever: Dengue fever is a mosquito-borne viral infection caused by the dengue virus, leading to symptoms such as high fever, severe headache, joint and muscle pain, and rash. This disease is classified as an emerging infectious disease due to its increasing prevalence in tropical and subtropical regions, raising concerns about its impact on public health globally.
Ebola Virus: The Ebola virus is a severe and often fatal viral infection that causes hemorrhagic fever in humans and nonhuman primates. This virus is a significant public health concern, particularly in Africa, where outbreaks can rapidly escalate, leading to high mortality rates and major social and economic impacts.
Endemic: Endemic refers to a disease or condition that is regularly found and consistently present within a specific geographic area or population. This persistent presence is often expected and can be measured in terms of baseline levels of infection, which helps public health officials understand the normal levels of disease occurrence and develop strategies for management and prevention.
Epidemiological Triangle: The epidemiological triangle is a model used to understand the factors that contribute to the spread of disease, consisting of three components: the agent, the host, and the environment. This framework helps public health professionals identify relationships between these components and how they interact to influence the occurrence of diseases, particularly during disease surveillance and outbreak investigation as well as in understanding emerging and re-emerging infectious diseases.
Globalization: Globalization refers to the process of increased interconnectedness and interdependence among countries, primarily in economic, cultural, and social dimensions. This phenomenon has significantly impacted the spread of ideas, goods, and services across borders, shaping global dynamics and health outcomes. The effects of globalization can be seen in how diseases emerge and spread, highlighting its crucial role in the context of public health.
Health disparities: Health disparities refer to the differences in health outcomes and access to healthcare that exist among different population groups. These disparities often stem from social, economic, and environmental factors that create inequities in health status and access to resources necessary for maintaining good health.
Herd Immunity: Herd immunity is a form of indirect protection from infectious diseases that occurs when a large percentage of a population becomes immune, either through vaccination or previous infections, thus reducing the overall spread of the disease. This concept is vital for protecting individuals who cannot be vaccinated, such as those with certain medical conditions, as it lowers their risk of exposure to the disease.
HIV/AIDS: HIV (Human Immunodeficiency Virus) is a virus that attacks the immune system, leading to AIDS (Acquired Immunodeficiency Syndrome), the most severe phase of HIV infection. This condition has a significant impact on global health, contributing to the burden of disease, particularly in vulnerable populations, and it requires robust responses to emerging and re-emerging infectious diseases, alongside addressing health security and adolescent health issues.
Multi-drug resistant tuberculosis: Multi-drug resistant tuberculosis (MDR-TB) is a form of tuberculosis (TB) infection that is resistant to at least the two most potent anti-TB drugs, isoniazid and rifampicin. This condition poses significant challenges for public health because it can lead to longer treatment durations, increased healthcare costs, and higher mortality rates. The emergence of MDR-TB highlights the importance of effective TB control programs and the need for new treatment options.
One Health Approach: The One Health Approach is a collaborative strategy that recognizes the interconnectedness of human, animal, and environmental health. It emphasizes that health issues are not isolated to one domain but rather involve complex interactions between humans, animals, and ecosystems, especially in the context of emerging and re-emerging infectious diseases.
Pandemic: A pandemic is an outbreak of a disease that occurs over a wide geographic area, affecting a large number of people across multiple countries or continents. This term is crucial in understanding how infectious diseases spread and the factors that contribute to their widespread impact on global health. Pandemics often emerge from pathogens that have adapted to new hosts or environments, leading to significant public health challenges and necessitating coordinated responses to control transmission.
Quarantine: Quarantine is the practice of separating and restricting the movement of individuals who may have been exposed to a contagious disease to prevent its spread. This public health measure is crucial during outbreaks, as it helps control disease transmission by isolating those who could potentially be infectious. Quarantine can apply to individuals who show no symptoms but may still carry the disease, making it essential for managing public health during infectious disease incidents.
Sars-cov-2: SARS-CoV-2 is a novel coronavirus that emerged in late 2019, responsible for causing the disease known as COVID-19. This virus is part of the coronavirus family, which also includes other pathogens that can lead to severe respiratory illnesses. SARS-CoV-2 quickly spread globally, leading to a pandemic that highlighted the vulnerabilities of public health systems and the importance of rapid response to emerging infectious diseases.
Surveillance: Surveillance is the systematic collection, analysis, and interpretation of health-related data to monitor the health of populations and identify public health threats. It plays a critical role in understanding disease trends, evaluating health interventions, and informing policy decisions, making it essential for effective public health practice.
Vaccination strategies: Vaccination strategies are organized plans designed to effectively implement immunization programs to prevent infectious diseases in populations. These strategies focus on maximizing vaccine coverage, targeting specific groups for vaccination, and addressing barriers to access, which is particularly important in managing emerging and re-emerging infectious diseases that can spread rapidly and have significant public health implications.
World Health Organization: The World Health Organization (WHO) is a specialized agency of the United Nations responsible for coordinating international public health efforts and addressing global health challenges. It plays a critical role in setting health standards, conducting research, and providing guidance to countries on various health-related issues, which links to numerous public health priorities and initiatives around the world.
Zika virus: Zika virus is a flavivirus primarily transmitted to humans through the bite of infected Aedes mosquitoes, particularly Aedes aegypti. This emerging infectious disease gained global attention due to its association with severe birth defects, particularly microcephaly, in babies born to mothers infected during pregnancy.
Zoonotic transmission: Zoonotic transmission refers to the process by which infectious diseases are transferred from animals to humans. This type of transmission is significant because many emerging and re-emerging infectious diseases have animal origins, leading to public health concerns as human populations interact more with wildlife and domesticated animals. Understanding zoonotic transmission helps in identifying potential outbreaks and implementing preventive measures.