GPH Quiz 3

One health

A collaborative, multisectoral approach that recognizes the health of people, animals, plants, and our shared environment are deeply interconnected

The Fourth Epidemiological Transition

• Represents an era of global ecological instability and hyper-connectivity

• Infectious disease dynamics are no longer just about isolated pathogens

• Direct products of broader socio-environmental systems, and public health must expand its focus to address the entire ecosystem, recognizing that human vulnerability is linked to planetary health

Human Health

Human wellness is inextricably linked to the broader ecosystem. Over 60% of all emerging infectious diseases in humans are zoonotic, originating directly from animal populations

Animal health

Animal populations act as primary reservoirs for zoonotic pathogens. Their health status directly dictates transmission dynamics and disease spillover risks to human populations

Environmental health

Environmental conditions heavily influence animal habitats and health. Ecosystem disruptions cascade directly and measurably across all three domains in the One Health framework

Feedback loops

• Human activities like deforestation and rapid urbanization actively sicken ecosystems

• These degraded environments place severe stress on local animal populations, compromising their immune systems

• Stressed animals subsequently shed higher viral loads and are forced to encroach on human habitats for survival

• This creates a dangerous feedback loop, directly driving zoonotic spillover events back into human populations

The dilution effect

• higher biodiversity in an ecosystem reduces the risk of pathogen transmission to humans or animals

• Demonstrates how high biodiversity functions as a protective biological shield

• In a diverse ecosystem, pathogens are distributed across a wide variety of host species

• Many of these diverse hosts act as “dead-end” hosts, meaning they are highly inefficient at transmitting the disease

• This ecological dilution significantly reduces the overall prevalence of the pathogen and lowers the transmission rate to humans

Amplification effect

• when an increase in biodiversity or specific host abundance leads to a net increase in disease or pathogen transmission risk.

• Ecological destabilization (mining or deforestation eliminating sensitive buffer species), reservoir survival (highly adaptable, human-adjacent species survive and thrive in the degraded environment), amplified risk (these surviving species are often excellent disease reservoirs, their dominance multiplies the risk of human infection)

Industrial food systems

• Rely on livestock populations that are densely packed and genetically uniform

• This genetic monoculture effectively removes natural immune resilience from the herd

• Without genetic variation, a single novel pathogen is more likely to rapidly sweep through a facility, devastating entire populations and creating massive viral loads at the human-animal interface.

Viral Reassortment

• The direct interface where displaced wildlife meets domestic livestock creates a dangerous biological “mixing vessel”, accelerating the pathogen’s ability to. cross species barriers

• In these shared environments, viruses from different species can easily interact, mutate, and exchange genetic material through reassortment

• This rapid evolutionary acceleration transforms a localized wildlife virus into an urgent agricultural and public health crisis

Reactive Human Medicine

Traditional public health relies on reactive medicine, waiting to treat sick humans after an outbreak occurs

Proactive Approach

• “One health”

• strategies prioritize actively considering animal and environmental health (predictive tracking of viral chatter, mapping wildlife migration patterns, continuous monitoring of ecological health indicators)

• Helps identify high-risk zones before human infection

Sentinel species

• by strategically monitoring unexplained animal die-offs or tracking specific wildlife diseases, scientists can gauge human outbreak risk

• Wildlife health functions as a highly accurate diagnostic tool for the broader ecosystems, providing critical lead time to implement public health interventions before human transmission begins

1999 Malaysian Nipah outbreak

• Agricultural expansion: Deforestation in Southeast Asia severely reduced natural forest habitats

• El Niño and fires from 1997-1998 in Indonesia

• Foraging crisis due to combined environmental catastrophe, decimated the natural foraging grounds and food supply of local wildlife

• Flying foxes (aka Pteropus fruit bats) are the natural, asymptomatic reservoirs of the virus, starving and displaced by destruction of their forest habitats, forced to migrate → relocated to densely populated agricultural zones in Malaysia, especially commercial fruit orchards

• Local farming practices involved planting commercial mango trees directly over or adjacent to open-air pig enclosures, and the migrating bats fed on this fruit, dropping virus-contaminated saliva, urine, and fruit into the pigsties below. The pigs consumed the contaminated fruit and virus rapidly spread through the dense herds, causing severe respiratory illness

• Occupational exposure drove human transmission as pig farmers inhaled aerosolized droplets from the coughing, infected pigs, the virus caused acute human encephalitis, resulting in devastating mortality rate of 40%

• Outbreak was only brought under control after the mass culling of over 1 million pigs, which collapsed a billion-dollar pig sector

Preventing future outbreaks

• One Health triad: focus on all aspects of the triad to prevent the environment and animals from causing virus outbreaks in humans, we are all connected and affect one another

Environmentalism

A social and political movement aimed at protecting the natural environment and promoting sustainable practices to ensure the well-being of both the planet and its inhabitants. Efforts are largely focused upon conservation and sustainability

Environmental Justice and the Environmental Justice Paradigm

Emphasizes that the benefits and burdens associated with environmental actions and policies should be equitability distributed across different social, racial, and economic groups

Vulnerability and health effects

• Environmental justice tackles the unequal impact of environmental hazards on vulnerable groups

• Certain populations are more exposed to the harmful effects of environmental hazards. this heightened vulnerability is a result of increased exposures or an innate susceptibility arising from social and biological factors

• Differs from environmentalism - Rachel Carson’s Silent Spring and DDT

Origin of Environmental Justice Movement

• Originated in the late 1980s, inspired by civil rights and other rights movements

• Aimed to address the skewed impact of environmental hazards on marginalized groups

Warren County PCB timeline

• 1978: Federal law requires that toxic waste be disposed of in a designated landfill (waste disposal is more costly as a result)

• 1979: In search of a cost-effective means to dispose of polychlorinated biphenyls (PCB) contaminated soil, NC selects the predominantly Black and poor community, Warren County, as the landfill site → Public hearing is held with nearly 800 protesters present

• 1982: The landfill is opened for operation Protesters were relentless in their opposition. Many were arrested “the largest civil disobedience in the South since Dr. Martin Luther King Jr. marched through Alabama”, predominantly African American residents protested the dumping of soil contaminated with PCBs in a landfill in their community, marked as the birth of the modern environmental justice movement

• 1994: President Bill Clinton signed an executive order requiring the federal government to account for the harm posed to minority communities by new hazmat disposal sites

• 2003: The Warren County landfill was closed

Michael S. Regan

Served as the 16th Administrator of the U.S. Environmental Protection Agency (EPA), making him the first Black man to lead the agency (2021-2024)

United Church of Christ Report (1987)

• The Commission for Racial Justice issued its landmark in 1987 report Toxic Wastes and Race in the United States

• The report was a church-sponsored study and one of the first to highlight the disproportionate placement of hazardous waste facilities in communities of color in the U.S. which provided statistical evidence for what many communities had long experienced

Flint Water Crisis (2014-Present)

In an effort to save money, the city of Flint, Michigan switched its water source, leading to lead contamination and a host of health issues. The predominantly black community has been vocal about the negligence and mismanagement that led to the crisis

Intersectionality

• Framework for understanding how various aspects of a person’s identity, such as race, gender, class, and other social categorizations, intersect and contribute to unique experiences of oppression or privilege

• Developed by Kimberlé Crenshaw in the lae 1980s, intersectionality highlights the complexity of social inequality, emphasizing that people can be disadvantaged by multiple sources of oppression that interact simultaneously

Uses of lead throughout history

• One of the first metals to be used by ancient societies, around 3000 B.C.

• Ancient Rome extensively utilized lead, they constructed water pipes from this metal, demonstrating their engineering prowess. In fact, our modern term ‘plumber’ traces its etymological roots back to the latin word “plumbum” which means lead

Lead exposures today

• Imported food cans

• doors and windows

• calcium supplements

• old plumbing fixtures

• lead in soil

• colored newspaper and bread wrappers

• old painted toys and furniture

• lead-based paint and pre-1978 houses

Primary sources of lead exposure

• lead dust from paint chips

• homes built prior to 1978

Exposure routes of lead

1. ingested by mouth

2. penetration through skin

3. inhalation into the lungs

Exposure risks: children vs. adults

• Preventable ‘silent’ exposure, children most vulnerable

• for children, many organs may be affected or more subtle brain function effects

Issue of generational equity lead and children

• Target organs behavioral effects seen in children less than 6 years old

• Brain cell damage in children usually not reversible

• Cells permanently lost

Lead exposure: health effects

• Blood effects: Hemoglobin synthesis disrupted, leading to anemia

• Red blood cell life span shortened: anemia, kidney effects

• Nervous system effects: myelin disintegrates, nerves to muscles in arms and legs affected, messages from brain to muscle affected, weakness

• Kidney effects: damage to tubular cells, kidney failure

• Bone effects: production of vitamin D altered, bone strength, lead stored in bones, bone formation affected

Interactions with diet

• Calcium is well known to decrease gastrointestinal lead absorption and thereby reduce the risk for lead poisoning

• Foods with calcium and iron protect the body against lead

Lead exposure symptoms

• headache

• irritability

• abdominal pain

• vomiting

• anemia

• weight loss

• poor attention span

• learning difficulties

• slowed speech development

• hyperactivity

• odds of failure to graduate from high school x7

Lead exposure: detroit

• ¼ children in Detroit estimated to be lead poisoned, low levels of screening

• We do not know what our pipes are made out of

• 1 of 6 lead-poisoned children suffers from learning and behavior problems

Lead Exposure: Cities in Pennsylvania

• Higher levels than Flint

• 10% of 140,000 children had elevated blood lead levels

Lead Exposure: Schools

• Elevated levels of lead have been found in schools across the US, alarming experts who say it is particularly harmful to children

• Of the 43% of districts that had tested, which cover 35 million students, more than 1/3 found lead (25 states and Washington DC test school water for lead)

Built Environment Intersects Social

• Lead pipes/infrastructure: City owned up to your property, then privately owned, disadvantaged areas lower levels of remediation (paint/pipes)

• Children in these neighborhoods disproportionately affected: low graduation, cyclical poverty

Cumulative Impacts: Vulnerability

Vulnerable populations are often simultaneously impacted by multiple environmental stressors, and therefore a source-by-source and pollutant-by-pollutant regulatory paradigm fails to adequately protect them

Mitigating Vulnerability

• Health impact assessments (HIA) provide a promising approach for incorporating cumulative impacts into assessments to guide decision making

• HIA is an interdisciplinary method for assessing the health impacts of proposed policies, plans, and projects

• Cumulative impact screening assessments highlight vulnerable communities that should be prioritized for interventions that improve existing conditions and prevent future harm

Neighborhood

• A geographically localized community or area within a larger city, town, suburb, or rural area

• Typically characterized by a unique sense of community, shared amenities, and often common cultural or historical traits

Neighborhood features and aspects

• Geographical boundaries: rivers or man-made roads

• Residential areas: contains living spaces like houses, apartments, etc.

• Commercial areas: local businesses, markets, shops, restaurants, etc.

• Public spaces: parks, playgrounds, community centers, other gathering spots

• Infrastructure: roads, bridges, public transport access, and other utilities

• Cultural or historical sites: landmarks, historical buildings, or other sites of significance

• Shared identity or characteristics: often, people in a neighborhood have shared experiences, cultures, traditions, or demographics

Operational Definition of Neighborhood

• Census Tracts are small, relatively permanent statistical subdivisions of a county or statistically equivalent entity, occasionally split due to population growth or merged as a result of substantial population decline

• Census tracts generally have a population size between 1,200 and 8,000 people, with an optimum size of 4,000 people

• The primary purpose of census tracts is to provide a stable set of geographical units for the presentation of statistical data

• Census tract boundaries are delineated with the intention of being maintained over a long time so that statistical comparisons can be made from census to census

Neighborhood Effects Theory

• The characteristics of a neighborhood or community, including its social structures and physical environment, have an impact on the residents’ behaviors, attitudes, and life outcomes

• It further suggests that the neighborhood in which a person lives can shape their opportunities, choices, and experiences, often independently of individual characteristics like age, race, or personal background

Study of neighborhood effects

• There are four basic research approaches to the study of neighborhood effects: Concentrated poverty, social processes and mechanisms, social observation, space-time analyses

Concentrated Poverty

• This approach focuses on areas where poverty is highly concentrated, examining how living in such areas affects residents in various ways compared to those living in more economically diverse or affluent neighborhoods

• Key Concepts: Economic segregation, resource deprivation, multi-generational poverty

• Research Focus: Studies may look at how concentrated poverty impacts educational outcomes, health, criminal behavior, social mobility, and other life outcomes. The emphasis is on understanding how the aggregation of poverty in a given area exacerbates negative outcomes

Economic Segregation

• Economic segregation isolates low-income populations from essential community wealth limits access to high-quality schools, transit, clean environments, and job networks

• Living in isolated neighborhoods fundamentally alters a resident’s long-term life trajectory compared to affluent areas. The gap in outcomes and the spatial gap between wealthy and impoverished areas continuously expands

• The systemic lack of local capital restricts upward social mobility, cementing disadvantage across generations

• Spatial segregation removes or dampens cross-class interactions, fewer interactions lead individuals to view existing disparities as more fair and less troubling.

Social Observation

• This approach is grounded in the idea that individuals’ behaviors and attitudes are shaped by observing and interacting with their neighbors

• Key concepts: role modeling, behavioral mimicry, social norms

• Research focus: for instance, researchers might study how exposure to neighborhood violence affects youths’ attitudes towards aggression or how the prevalence of college-educated adults in an area influences educational aspirations among local youth

Fagan (2014)

• Data from about 1,661-1,718 adolescents

• diverse in terms of sex (51% male, 49% female)

• race/ethnicity (48% hispanic, 34% african american, 14% caucasian, and 4% other)

• age (mean age 12 years; range 8-16)

• youth who witnessed or experienced a greater variety of violent acts had a significantly greater likelihood of violence in the past year

Social Processes and Mechanisms

• This perspective examines the underlying social dynamics and processes within neighborhoods that influence individual outcomes

• Key concepts: social cohesion, collective efficacy, social networks, peer influence

• Research focus: Investigations might explore how trust and collaboration among residents affect crime rates, how local social networks impact job opportunities, or how neighborhood norms influence individual behaviors and aspirations

Social Cohesion and Depression

• Social support, collective efficacy, trust, safety, and positive social relations are dimensions of neighborhood social cohesion that may reduce feelings of isolation, improve emotional regulation, and strengthen resilience

• Higher neighborhood social cohesion is associated with lower risk of subsequent depression

• Initiatives that foster engagement, such as the creation of accessible public spaces or implementing community activities, can increase levels of social cohesion which may in turn protect neighborhood members from depression

Space-Time Analysis

• This approach examines neighborhoods as dynamic entities that change over time and space, taking into account both historical context and spatial relationships

• Key concepts: spatial autocorrelation (how one area is influenced by adjacent areas), temporal trends, neighborhood change and evolution

• Research focus: research might explore how gentrification changes neighborhood characteristics over time or how the spatial arrangement of resources (like schools or parks) influences residents’ access and outcomes

• Tobler’s First Law of Geography: “everything is related to everything else, but near things are more related than distant things”

Neighborhoods and health

• The study of neighborhoods and health outcomes underscores the intricate relationship between environment and well-being

• The spatial contexts in which individuals reside exert profound influences on their health, both directly and indirectly

• Through the interplay of socio-economic factors, access to resources, social networks, and environmental conditions

Built environment

Affects health through various pathways

• facilitating or impeding physical activity

• providing or impeding access to healthy foods and jobs

• improving or degrading air quality

• promoting social interaction or aggravating social isolation

History of cities

• Early cities were established along trade routes or at points where the movement of goods shifted from one mode of transportation to another, such as at river and ocean ports

• Early population hubs often developed around a central public plaza

• The main form of travel was walking, so people needed to live near where they worked, traded, and prayed; compact, high-density settlement was the norm

• The need to move goods and people locally led to the development of street networks for use by wagons and carriages

Industrialization and cities

• Industrialization in nineteenth-century Europe, North America, and certain other places brought an influx of manufacturing jobs and workers into cities

• These fast-growing cities featured crowded, squalid conditions and inadequate infrastructure, facilitating the spread of diseases such as tuberculosis and typhoid

The Sanitary Movement (Late 19th Century)

• In response to rapid urbanization and its health impacts

• Public health professionals investigated infectious disease transmission in cities, and they focused their attention on urban planning, public infrastructure, and housing quality

• Formative stage in public health history, now referred to as the sanitary movement

• Public health, housing, and architecture: professionals from all three fields come together to address health risks in urban spaces

Immigrants and African Americans in Large Cities

• Millions of immigrants from Europe between 1880s and 1920s migrated to the U.S. for work and better life opportunities

• 1910-1940 the great migration of African Americans from southern states to northern and midwestern cities during the twentieth century accelerated urban growth, with unprecedented concentrations of poverty in urban centers