Ch_19_lecture

Epidemiology

The scientific discipline that studies how diseases and health conditions spread within populations, investigating the causes, effects, and control measures through data analysis to inform public health policies and interventions.

Portal of exit

The pathway that a pathogen uses to leave its host before spreading to another individual, which can include respiratory secretions (like coughing), blood, urine, and various bodily fluids.

Portal of entry

The routes through which a pathogen gains access to a new host, including mucous membranes, broken skin, and the respiratory tract.

Communicable diseases

Illnesses caused by infectious agents that can be transmitted from one person to another through various modes such as direct contact, respiratory droplets, or vector carriers.

Non-communicable diseases

Health conditions that cannot be transmitted between individuals, typically characterized by chronic issues such as diabetes, heart disease, and certain forms of cancers.

Morbidity rate

The frequency of disease occurrence in a population, expressed as the number of new and existing cases within a specified period relative to the population at risk. This differs from mortality rate, which solely counts deaths.

Mortality rate

The frequency of death in a defined population over a specific time frame, commonly expressed per 1,000 or 100,000 individuals, indicating the severity of health issues.

Incidence

A measurement of new cases of a particular disease occurring within a specific population during a defined time period, reflecting the risk or rate of developing that disease.

Prevalence

The total number of individuals currently affected by a specific disease within a population at a given time, providing insight into the overall burden of that disease.

Endemic

A disease that is consistently present within a specific geographic area or population, maintaining a steady state of infection over time.

Epidemic

A sudden increase in the number of disease cases above what is normally expected in a specific geographic area or among a certain group of people.

Outbreak

A sudden rise in disease cases within a localized area, often used interchangeably with 'epidemic,' although typically referring to smaller scales.

Pandemic

An epidemic that has spread across multiple countries or continents, affecting a large number of people and often causing widespread health and social impacts.

Reservoir

Any natural habitat or carrier that harbors pathogens capable of causing disease, including humans, animals, and environmental sources such as soil or water; for instance, bats for rabies and rodents for hantavirus.

Symptomatic infection

An infection where the host exhibits clinical signs and symptoms of the disease, aiding in diagnostics and treatment.

Asymptomatic carriers

Individuals who are infected with a pathogen but do not show symptoms, yet can still transmit the disease to others.

Zoonoses

Infectious diseases that are transmitted from animals to humans, with examples including rabies, West Nile virus, and particular strains of influenza.

Horizontal disease transmission

The transfer of pathogens between individuals of the same species within the same generation, often through direct contact or environmental sources.

Vertical disease transmission

Transmission of pathogens from parent to offspring, occurring during pregnancy, childbirth, or breastfeeding.

Fomites

Inanimate objects or surfaces that can carry infectious agents, facilitating their transmission; examples include doorknobs, utensils, and medical equipment.

Droplet nuclei

Small respiratory particles that remain airborne after the larger droplets have evaporated, capable of transmitting infections over longer distances.

Vectors

Living organisms, typically arthropods like mosquitoes and ticks, that can carry and transmit pathogens to humans or other animals.

Mechanical vectors

Organisms that physically carry pathogens from one host to another without undergoing any development or multiplication of the pathogen; for example, flies contaminating food.

Major portals of exit and entry

The primary pathways for pathogens to exit and enter hosts, including respiratory secretions, gastrointestinal tract secretions, blood, skin, and through mucous membranes.

Factors influencing disease epidemiology

Key elements that affect disease epidemiology, including environmental conditions, host factors (such as genetics and immunity), social behaviors, and access to healthcare.

Descriptive epidemiological studies

Studies that focus on the characteristics of affected populations, providing insights into the who, what, where, and when of health-related events.

Analytical epidemiological studies

Studies designed to understand the 'why' and 'how' of health patterns by examining relationships between exposures and outcomes.

Experimental epidemiological studies

Research that tests hypotheses and involves interventions, focusing on the effectiveness of treatments or prevention strategies.

Risk factor

Any attribute, characteristic, or exposure that increases the likelihood of developing a disease or health condition.

Placebo

A substance or treatment with no active therapeutic effect, often used in clinical trials for comparison against active treatments.

Double-blind study

A study design in which neither the participants nor the researchers know which participants are receiving the treatment or placebo, thereby reducing bias in the results.

Cross-sectional study

A study that assesses the relationship between exposure and outcome in a population at a single point in time, providing a snapshot of the health status.

Retrospective (Case-Control) study

A study examining past exposure to risk factors in individuals with a disease (case group) compared to those without the disease (control group) to identify potential causes.

Prospective study

A study that follows a group of individuals over time to see how different exposures affect health outcomes, starting before any disease has developed.