Emerging Infectious Disease

Infectious diseases—caused by pathogens such as viruses, bacteria, fungi, or parasites—pose a latent but persistent threat to public health, economic stability, and societal functioning. Within the BRADD region, outbreaks (whether seasonal, emerging, or re-emerging) have the potential to disrupt daily life, strain healthcare systems, and interrupt essential services. The risk may come from influenza, novel respiratory viruses, vectorborne illnesses, foodborne pathogens, or other contagions. While many outbreaks are mitigated through public health measures (vaccination, surveillance, infection control), the possibility of a local epidemic or pandemic cannot be disregarded. In assessing infectious disease as a hazard, it is essential to evaluate both the inherent transmissibility of pathogens and the local factors (population demographics, healthcare capacity, social behavior) that influence spread, severity, and resilience.

Description Extent, Past Events, & Location Probability Impact Vulnerability Summary Analysis

What is an Emerging Infectious Disease?

An Emerging Infectious Disease (EID) is an emerging or re-emerging virus that has not reached the level of a pandemic. EIDs may primarily infect smaller pockets within a larger community due to some population immunity or limited contact. Because it has not reached a level of pandemic and, thus, fewer people have been infected, there will be more resources available to aid in response and recovery.

The Baylor University College of Medicine defines Emerging Infectious Disease, or EID, as “infections that have recently appeared within a population or those who incidence or geographic range is rapidly increasing or threatens to increase in the near future”. Recent outbreaks that have been classified as EID were SARS, MERS, Ebola, chikungunya, avian flu, swine flu, and zika. EIDs are an important consideration for public health professionals and local elected officials because they have been the cause of some of the deadliest pandemics in history, such as the 1918 Spanish Influenza and the HIV/AIDs outbreak.

Causes of Emerging Infectious Disease

There are four primary causes for the emergence and spread of an infectious disease per the Baylor College of Medicine:

  1. Previously undetected or unknown infectious agents
  2. Known agents that have spread to new geographic locations or new populations
  3. Previously known agents whose role in specific diseases have previously gone unrecognized
  4. Re-emergence of agents whose incidence of disease had significantly declined in the past, but whose incidence of disease has reappeared. This class of diseases is known as re-emerging infectious diseases.

How do Emerging Infectious Diseases Spread?

There are a myriad of ways in which EIDs can spread to and throughout the population. This subsection explores them by dividing them into two categories: direct versus indirect contact.

Direct Contact

Direct contact refers to when an individual is infected by another person or an animal that has the disease.

  • Person to Person: Person to person disease spread occurs when an individual makes direct contact with someone who has already contracted the disease through kissing, hugging, touching, coughing, or sneezing.
  • Animal to Person: Animal to person transfer can occur if a person is either bitten or scratched by an infected animal. Spread can also occur by handling animal waste.
  • Mother to Unborn Child: Germs that cause infectious disease can be spread to an unborn child while it is still in the womb by passing through the placenta or it can be transmitted during birth.
Indirect Contact

Indirect infectious disease spread occurs when the infection is spread through an inanimate object or by something that has not contracted the illness, but is simply a host.

  • Insect Bites: Some infectious diseases, such as malaria, are carried by insects and spread through bites. The insects that act as hosts to the disease is known as a vector.
  • Food Contamination: Food and water may be contaminated by a germ and human consumption is the point of contamination.

Extent

The extent of an infectious disease outbreak depends on the pathogen’s mode of transmission, incubation period, and available countermeasures such as vaccines or antiviral treatments. Outbreaks may range from localized clusters of illness to regional or global pandemics causing widespread morbidity and mortality. Diseases transmitted through airborne or droplet routes—such as influenza or COVID-19—tend to spread more rapidly and have greater potential to overwhelm healthcare capacity than vectorborne or foodborne illnesses. The overall severity of an event is determined by its transmissibility (R₀ value), case fatality rate, and duration of community disruption. In the BRADD region, future outbreaks are likely to vary in magnitude from short-term, seasonal illness surges to prolonged public health emergencies that strain hospitals, supply chains, and essential services.

Past Events

The BRADD region, like much of Kentucky, has experienced multiple infectious disease events of varying scope and severity. Seasonal influenza outbreaks occur annually and periodically cause elevated absenteeism and strain on healthcare facilities. The 2009 H1N1 influenza pandemic resulted in widespread community transmission and increased vaccination demand. Most recently, the COVID-19 pandemic (2020–2022) produced extensive social, economic, and health impacts, testing the capacity of local hospitals, long-term care facilities, and public health departments. The region has also observed smaller-scale outbreaks of gastrointestinal illness, hepatitis A, and tick-borne diseases. These past events illustrate the recurring nature of infectious disease hazards and the importance of sustained preparedness and public health coordination.

Probability

The probability of future infectious disease events in the BRADD region is high. While large-scale pandemics are less frequent, seasonal and emerging diseases occur regularly and have demonstrated the ability to disrupt community life. Population mobility, interstate travel, and the presence of schools, workplaces, and congregate facilities increase the likelihood of pathogen introduction and spread. Climate trends that affect vector populations, along with global connectivity and evolving pathogens, further elevate risk. Although improved surveillance, vaccination programs, and public health planning mitigate some risk, infectious disease remains among the most consistently probable hazards facing the region.

Impact

An infectious disease outbreak in the BRADD region could cause a spectrum of impacts, ranging from mild illness to widespread morbidity and mortality, depending on the pathogen’s virulence, transmissibility, and available countermeasures. Impacts would likely include increased hospitalization and demand on medical and emergency services, absenteeism in essential and critical workforces, disruption of commerce and supply chains, and strain on public health resources. Secondary impacts may include economic losses from business closures, school interruptions, reduced consumer activity, and mental health stresses. Vulnerable populations—such as older adults, those with chronic illnesses, and uninsured or underserved groups—may experience disproportionate harm. Even after the acute phase, lingering effects such as long-term health consequences, reduced community confidence in public systems, and health equity issues may persist.

Emerging infectious diseases can indirectly impact the built environment through strain on healthcare facilities, temporary closure of public buildings, and disruption of essential infrastructure operations. During outbreaks, maintenance of utilities, transportation systems, and public facilities may be reduced due to workforce shortages or infection control measures. Prolonged outbreaks can delay construction projects, affect supply chains, and create deferred maintenance in public buildings. While direct physical damage is uncommon, the built environment may require adaptations—such as improved ventilation, enhanced sanitation systems, and spatial modifications—to support public health resilience.
The natural environment can influence and, in turn, be affected by emerging infectious diseases. Vectorborne and zoonotic diseases are often linked to ecological conditions such as wildlife migration, deforestation, water quality, and climate variability. Outbreak response efforts may also produce temporary environmental impacts, including increased medical waste generation or chemical disinfection runoff. Long-term shifts in land use, biodiversity, and temperature patterns can alter disease transmission dynamics, emphasizing the interconnectedness of environmental stewardship and public health protection.
Emerging infectious diseases have the most profound and lasting impacts on the social environment. Outbreaks can disrupt daily routines, isolate communities, and heighten anxiety and misinformation. School closures, job losses, and restrictions on gatherings reduce social cohesion and strain mental health. Vulnerable populations—such as older adults, low-income households, and those with limited healthcare access—experience disproportionate effects. Recovery requires rebuilding trust in public systems, restoring community networks, and promoting health equity through education, communication, and long-term resilience planning.
With the onset of changing weather patterns, distribution of vegetation and vectors that spread disease (e.g., ticks, mosquitoes, rats, etc.) are likely to expand or move geographically to unimpacted areas. Additionally, changes in living conditions and population migration to take refuge from impacts like heat and water stress could also bring risk of new diseases and higher rates of infection to certain regions. Recent disease outbreaks caused from humans interacting with infected species has caused the spread of virus and other pathogens from hosts to humans, which can be exacerbated as species interactions occur due to increasing climate pressures. Additionally, population growth and increased development, combined with more frequent storms and changes in rainfall patterns, may increase the population of mosquitoes and other vectors that thrive in certain climates that typically do not do well in the region under the current climate regime.

The BRADD region is at moderate risk for an increase in vector-borne illness as climate patterns shift and milder, warmer winters allow for the spread and invasion of ticks and insects. Additionally, a lower risk exists due to population pressures on agriculture and other natural habitats, which could increase proximity of both human-human and human-animal interactions and allow for the spread of disease.

Potential impacts include:
  • increase in infectious disease via vector
  • emerging pathogens from host transfer or new disease spread in the region by vector
  • increase in infectious disease via human-human contact

Vulnerability

Across the BRADD region, vulnerability to infectious disease is shaped by factors including population density, age structure, access to healthcare, and mobility patterns. Urban and semi-urban counties with hospitals, congregate settings (e.g. long-term care, prisons, schools), and higher population turnover may face greater exposure and transmission potential. Rural areas may face challenges in accessing care, diagnostics, or public health infrastructure, compounding vulnerability if an outbreak reaches them. Counties with more aging populations or higher prevalence of underlying health conditions (e.g. diabetes, heart disease) may suffer higher morbidity and mortality rates. Gaps in vaccination coverage, health literacy, and public health capacity can amplify risk. Interjurisdictional coordination, surveillance, and rapid response capability are therefore critical to reducing vulnerability across the region.

Vulnerability Summary Analysis

The degree of vulnerability to infectious disease varies among BRADD’s ten counties based on differences in population density, healthcare infrastructure, mobility, and demographic composition. Urbanized counties with larger populations and medical centers face greater exposure potential but often possess stronger health resources for response and recovery. Conversely, rural counties may experience delayed detection and limited access to care, compounding impacts once disease transmission occurs. The following summaries describe each county’s relative vulnerability and highlight key considerations for preparedness and mitigation.

Allen County’s vulnerability to infectious disease is moderate. The county’s smaller population and lower density reduce transmission acceleration, but health care and diagnostic resources are limited. Scottsville and surrounding unincorporated areas may have populations with longer travel times to hospitals or specialty care. If a contagious pathogen enters the community, limited surge capacity in local clinics or hospitals may constrain prompt response and case isolation.
Barren County faces elevated vulnerability due to its larger population base (Glasgow area), medical facilities, schools, and businesses that attract people from surrounding counties. The presence of regional health institutions and higher connectivity may both aid in disease detection and increase exposure risk. The county’s public health infrastructure must be capable of rapid vaccination, testing, and contact tracing to guard against escalation.
Butler County’s rural character and lower population density confer some natural dampening of transmission risk, but infrastructure constraints may amplify vulnerability in an outbreak. The county may lack redundancy in diagnostic laboratories, emergency care, or isolation capacity. Delays in health services or public health response could worsen outcomes, especially for more severe pathogens.
Edmonson County’s vulnerability is influenced by its tourism assets (e.g. Mammoth Cave National Park). Seasonal influxes of visitors may introduce pathogens or increase transient mixing, raising exposure risk. However, local health infrastructure is limited, and access to advanced care is likely located in adjacent counties. Surveillance, partnerships with park authorities, and cross-county coordination are key in managing outbreak introduction.
Hart County’s vulnerability is moderated by mixed rural/transportation attributes. The county’s highways, visitor traffic, and local attractions may contribute to pathogen importation risk. However, the dispersed population and fewer congregate facilities limit explosive person-to-person spread in the early phase. Nonetheless, once introduced, resource constraints may hamper containment and treatment efforts.
Logan County’s vulnerability is relatively higher among the more rural counties owing to its role as a regional hub in parts of the region (Russellville). With clinics, local hospitals, and intercounty interaction, transmission chains could propagate if detection or containment is delayed. High prevalence of chronic health conditions may increase the severity of disease outcomes in vulnerable segments of the population.
Metcalfe County’s vulnerability is lower in terms of rapid transmission potential due to smaller population and lower density. However, limited healthcare infrastructure and diagnostic capacity may slow detection and response, allowing outbreaks to expand before containment. The county would rely heavily on regional support for laboratory services, surge staff, and public health resources.
Monroe County’s vulnerability is shaped by its border proximity and rural character. Cross-county mobility (especially across state lines) could introduce pathogens. Tompkinsville’s medical and public health resources may be stretched if outbreak dynamics intensify. Slower communication and logistical challenges in remote areas may affect testing, tracing, and isolation efforts.
Simpson County faces intermediate vulnerability due to its proximity to larger population centers and connectivity via Interstate 65. Commercial, industrial, and commuter movement through the county raises the chance of importation and spread. The presence of institutional settings (schools, workplaces) means that early detection and mitigation protocols are especially important to prevent clusters from growing.
Warren County has relatively high vulnerability in the BRADD region due to Bowling Green’s urban scale, university presence (Western Kentucky University), and concentration of healthcare, commerce, and transportation. The potential for rapid spread in congregate settings (residences, dorms, offices, public transit) is significant. However, the county also typically holds stronger public health infrastructure, hospital systems, and laboratory capacity. Continuous vigilance, vaccination outreach, and surge planning are essential to defend against major outbreaks.