Epidemiology and Disease Transmission

Vocabulary flashcards covering key terms related to epidemiology, disease outbreaks, and transmission dynamics, based on lecture notes.

Epidemiology

The branch of medicine studying the distribution, determinants, and control of diseases in populations.

Disease Outbreak

An occurrence of disease cases in a population greater than what is expected.

Epidemic

A situation where an infectious disease spreads rapidly and affects a large proportion of the population within a specific region.

Pandemic

An epidemic that extends across countries or continents, affecting a large number of people.

R₀ (Basic Reproductive Number)

The expected number of secondary infections that one infected individual will cause in a completely susceptible population.

Rt (Effective Reproductive Number)

The average number of secondary infections caused by an infected individual at a specific point in time during an outbreak.

R₀ Role

The initial measure of a disease’s potential to spread in a population at the start of an epidemic.

Rt Role

Calculated later in the epidemic, typically less than R₀ due to interventions and immunity.

Decreasing Susceptibility

Becoming infected or vaccinated.

Reduced Contacts

Social distancing, quarantine, and isolation.

Behavioral Changes

Ill people reduce contact, and healthy people avoid ill people.

Syphilis

Caused by the bacterium Treponema pallidum, which is typically transmitted through sexual contact.

Syphilis in Olive Baboons

Genital lesions in the baboons suggest the possibility that syphilis could also be a sexually transmitted infection (STI) in non-human primates.

Female Avoidance

Related to avoidance of mates with ulcers.

Avoidance of Infected Individuals

Behavior seen in many species to reduce the transmission of diseases.

Anti-Parasitic Treatment and Social Behavior

Tend to groom anti-parasitic treated individuals more.

Feces Avoidance

Likely due to distinct odor associated with infection.

Behavioral Impact of Parasitic Infection

Adaptive behavior to prevent the spread of parasitic infections within the group.

Sickness Behavior

A set of behavioral changes that occur in individuals who are sick.

Inactivity

A decrease in physical activity as the body rests and tries to recover.

Reduced Food Intake

Reduced appetite and food consumption.

Postures to Conserve Heat

Decreased activity levels to conserve body heat and energy.

Increased Sleep

Sleepiness and reduced energy levels to aid in recovery.

Sickness Behavior in Humans

Sick humans often isolate themselves from others.

Social Isolation

Infected individuals are often socially isolated by others.

Isolation

The separation of individuals who are known to be infected with a contagious disease from those who are healthy.

Quarantine

The separation of individuals who have been exposed to a contagious disease but are not yet showing symptoms.

Leviticus 13:46 (300-500 BCE)

Biblical texts describing isolation practices for individuals with diseases.

Leprosy

Individuals infected with leprosy were isolated in 'leper colonies'.

Homogeneous Population

Assumes that everyone in the population has an equal chance of being infected.

Homogeneity

Everyone in the population has the same level of contact with others.

Condition for Spread

For a disease to spread in a homogeneous population, the basic reproductive number R₀ must be greater than 1.

Epidemic Spread

If R₀ > 1, the disease will spread exponentially.

Environmental Impact on Disease Transmission

Some pathogens are more stable and transmissible under specific environmental conditions.

Temperature and Humidity

Some pathogens are more stable and transmissible under specific environmental conditions like temperature and humidity.

Malaria (Seasonal Diseases)

The transmission of malaria increases during the rainy season when mosquito populations are high.

Influenza (Seasonal Diseases)

Flu transmission peaks in colder months when people tend to gather indoors.

Sleeping Sickness (Vector-Dependent Diseases)

The incidence of sleeping sickness is linked to the rainy season when tsetse fly populations are highest.

Bacteria Examples

Tuberculosis (Mycobacterium tuberculosis) and Cholera (Vibrio cholerae).

Viruses Examples

HIV/AIDS, Influenza, and SARS-CoV-2.

Protozoa Examples

Malaria (Plasmodium spp.) and Sleeping Sickness (Trypanosoma brucei).

Fungi Examples

Candidiasis (thrush) and Aspergillosis.

Macroparasites Examples

Helminths (roundworms, tapeworms) and Arthropods (lice, fleas, ticks).

Prions Examples

Bovine Spongiform Encephalopathy (mad cow disease), a degenerative neurological disease caused by misfolded proteins.

Malaria Transmission

Plasmodium species are transmitted to humans by infected female Anopheles mosquitoes.

Impact of Malaria

Malaria remains one of the most deadly infectious diseases globally.

Epidemiology

Branch of medicine that studies the distribution, determinants, and control of diseases in populations

Disease Outbreak

Occurrence of disease cases in a population greater than what is expected.

Epidemic

Infectious disease spreads rapidly and affects a large proportion of the population within a specific region.

Pandemic

Epidemic that extends across countries or continents, affecting a large number of people.

R₀

Expected number of secondary infections that one infected individual will cause in a completely susceptible population.

Rt

Average number of secondary infections caused by an infected individual at a specific point in time during an outbreak.

R₀ (initial)

Measure of the disease’s potential to spread at epidemic's start.

Rt (later)

Calculated later, less than R₀ due to interventions and immunity.

Decreasing susceptibility

Becoming infected or vaccinated reduces susceptible population.

Reduced contact

Social distancing, quarantine, isolation reduce interactions.

Behavioral changes

Sick avoid others; healthy avoid sick to reduce spread.

Syphilis cause

Bacterium Treponema pallidum, typically sexually transmitted.

Baboon syphilis

Genital lesions suggest potential STI in non-human primates.

Female avoidance

To avoid infection, females avoid males with genital ulcers.

Avoidance of infected

Common in species to reduce disease spread.

Antiparasitic treatment effects

Treatment increasing grooming may reduce infection risk.

Feces avoidance

Distinct odor likely causes avoidance.

Behavioral impact

Adaptive parasitic spread prevention.

Sickness Behavior

Behavioral change set with illness.

Inactivity (sickness)

Physical activity reduced.

Reduced food intake

Appetite reduced.

Conserve heat

Decreased activity to conserve energy.

Increased sleep

More sleep to aid recovery.

Sick human isolation

To reduce spreading disease through rest.

Social isolation

By population; prevents spread.

Isolation

Separation of infected from healthy.

Quarantine

Separation of exposed from healthy.

Leviticus quarantine

Disease isolation in ancient texts.

Medieval leprosy isolation

Lepers kept isolated.

Homogeneous population

Equal infection and contact chance in population.

Spread condition

R₀ greater than 1 for disease spread.

Epidemic spread

Cases increase exponentially when R₀ greater than 1.

Environmental impact

Pathogens stable/transmissible depending…

Temperature & humidity impacts

Pathogen stability affected.

Malaria seasonality

Rains increase malaria through mosquitoes.

Influenza seasonality

Indoor flu spread increased in cold.

Sleeping sickness vector

Rain increase fly, increasing trypanosomiasis.

Bacteria example

Tuberculosis, Cholera.

Virus example

HIV, Influenza, SARS-CoV-2.

Protozoa examples

Malaria, sleeping sickness.

Fungi example

Thrush, Aspergillosis

Macroparasite example

Round/tapeworms, lice, fleas

Prion example

Mad cow disease.

Malaria transmission

Anopheles transmits

Malaria impact

Global infectious disease.

Epidemiology

Study of disease distribution, causes, and management in populations.

Disease Outbreak

More disease cases in a specific place and time than expected.

Epidemic

Fast spread of disease impacting many in a region.

Pandemic

Disease epidemic that spans across multiple continents/countries.

R₀ (Basic Reproduction Number)

Expected count of new cases from one infected person in a completely defenseless population.

Rt (Effective Reproduction Number)

Average count of new cases from one infected person during an outbreak.

R₀ role

R₀ measure early in the outbreak; spread potential.

Rt Role

Rt is determined later, reflecting interventions like quarantine; less than R₀

Decreased Susceptibility

Population immunity rising through vaccination/infection, reducing spread.