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Epidemiology
The study of the distribution, dynamics, and determinants of disease.
Distribution of Disease
Demographic and geographic distribution of diseases.
Dynamic of Disease
Mode of transmission of diseases within a population.
Infection
The first step when a microbe enters the body and begins to multiply. The state when a microorganism becomes established in the host and clinically detected.
Disease
The state when cells in the body become damaged as a result of infection and signs and symptoms appear.
Infectivity
The ability of a pathogen to infect a host.
Contagious disease
Any disease that is transmitted from person to person.
Basic Reproduction Number
A mathematical term indicating how contagious an infectious disease is.
Incubation period
The time between exposure to a pathogen and the appearance of the first symptoms.
The incubation period is dependent on:
The specific pathogen and the body’s response systems.
Carrier
A person infected with a microorganism but shows no symptoms and can pass the disease onto others.
Pathogen
Any microorganism that can cause disease.
Bacteria
Single-celled organisms that can cause various diseases and can be classified by shape.
What is an example of a cocci (round) bacteria?
Streptococcus (A or B)
Staphylococcus
What is an example of a bacillus (capsule) bacteria?
E. coli.
Viruses
Infectious agents that require a host to reproduce and can cause a variety of diseases.
Structural components of viruses:
The core contains nucleic acid
The capsid or protein coat protects the nucleic acid
The membrane envelope covers the protein coat
Bacteriophage
A virus that infects and replicates within bacteria.
What are the general steps in the reproduction of virus particles?
Virus attaches to host cell
Virus penetrates host cell membrane and injects nucleic acid into cell
Viral nucleic acid replicates using host cell machinery
New viral nucleic acids are packaged into viral particles and released from the cell
Prion
An infectious agent made of protein that can cause infections leading to neurodegenerative diseases.
Kuru
A disease caused by prions and spread via funerary cannibalism in Papua New Guinea.
Protozoa
Single-celled organisms that can cause diseases like malaria.
What is an example of a protozoa?
Malaria.
Fungi
Organisms that can cause plant and animal diseases, including infections in humans.
A modern day drug derived from fungi.
Penicillin.
How can fungi reproduce and what infections can they cause?
They reproduce through tiny spores in the air, leading to infections on the skin and inhaled into the lungs.
Parasites
Organisms that live within or on a host and use the host's resources to fuel their life cycles.
Symbiotic Relationship
A relationship between two species where both benefit.
Commensal Relationship
A relationship between two species where one benefits and the other remains unaffected.
Parasitic Relationship
A relationship between species where one benefits and the other is being harmed.
Pathogenicity
The ability of a microorganism to cause disease.
Virulence
The degree of pathogenicity of a microorganism.
The degree to which a pathogen causes serious illness or death is dependent on:
The immune system of the host
The number of pathogenic microorganisms encountered
The nature of the pathogen
Direct contact
Transmission of diseases through physical contact; mother to fetus, airborne transmission, skin contact.
Indirect contact
Transmission of diseases through vectors, food, water, or other means.
Horizontal Transmission
Transmission from one individual to another.
Vertical Transmission
Transmission directly from parent to offspring before or directly after birth.
Susceptibility
An individual's risk for infection.
Resistance
The infected individual's capacity to prevent infection from leading to disease and death.
Immunity
Resistance to disease, either innate or acquired.
Innate Immunity
Genetic factors, the first line of defence.
Acquired Immunity
The specific immune response where the microbe gets past the innate immune system.
Herd Immunity
A type of immunity where a significant proportion of a community is immune to a contagious disease, whether through immunization or prior exposure.
The immune system
The body's natural defense system against pathogens.
Paleopathology
The study of past diseases in human remains.
Ethnography
An anthropological study through personal accounts and scientific descriptions of customs.
Sources of information on health and disease:
Ethnography
Paleopathology
Ancient text
Art
Characteristics of Hunter-gatherer societies:
A variety of foods (seasonal foods)
Smaller groups
Contact between groups is limited
Lower population density
Nomadic, highly mobile people
No class distinctions
Diseases that Plagued Early Hunter-Gatherers:
Insect bites (Malaria)
Diseases from other animals (Rabies)
Chronic infections (acute food poisoning)
Physical trauma
Congenital diseases (joint disease)
Seasonal famines
External parasites (lice)
Zoonotic Diseases
Diseases that can be transmitted from animals to humans.
Social Stratification
The division of society into different social classes.
Agricultural Practices
The methods and techniques used in farming and agriculture.
Epidemiological Transitions
Shifts in the patterns of diseases and health conditions in populations over time. Agriculture, medical treatments, and re-emergence of infectious diseases.
Noncommunicable Diseases (NCD)
Diseases that are not caused by infectious agents and cannot be transmitted from person to person.
Chronic disease
A disease that cannot be passed from person to person and lasts for a long period of time.
Yersinia Pestis
The bacteria that causes the plague.
Alexandre Yersin
The scientist who discovered the Plague in Hong Kong, 1884.
Bubonic Plague
The most common form of the plague, characterized by swollen lymph nodes and spread through flea bites.
Pneumonic Plague
A more virulent form of the plague that affects the lungs and is spread through inhaling air particles or contact with infected individuals.
Septicaemic Plague
A form of the plague that enters the bloodstream and causes severe symptoms, including internal bleeding and a high fatality rate.
What non-human carriers spread the Plague?
Rats, human fleas, and lice.
Xenopsylla cheopis
The oriental rat flea, responsible for spreading the plague by biting humans and regurgitating infected rat blood into open wounds.
Antibiotics for the Plague
Medications used to treat bacterial infections, including streptomycin, doxycycline, gentamicin, and ciprofloxacin.
Symptoms of the Bubonic Plague:
Sudden high fever
Headache
Body aches and chills
Swollen, painful lymph nodes causing “bubos” lumps
Incubation period of the Bubonic Plague
2-7 days.
Origin of the Plague
The Bronze Age in Russia.
Plague of Justinian
A plague pandemic that occurred from AD 541-44 and continued intermittently until 750, possibly originating from China and North East India.
The Black Death
The most well-known and devastating plague pandemic that occurred from 1346-1361, spreading across Europe and causing the death of millions of people.
The Great Plague of London
A plague outbreak that occurred in 1665 in London, causing a high number of deaths and leading to significant social and economic transformations.
The fortress of Kaffa
The first possible case of biological warfare between the Italian Christians and the Muslim Mongols.
The origin of quarantines
The Italian word for 40, the number of days Italian ships were isolated upon arrival to new ports.
Third Plague Pandemic/China-California
A plague pandemic that occurred from 1894-1924, originating in China and spreading to other parts of the world, including India and Australia.
Theory of Contagion
Spread of disease between person to person and object to person.
Theory of Miasma
Spread of disease via “bad air”.
Mortality of the Plague
Killed ~30 million people in Europe, 1/3 of the population at the time.
The Flagellants
Travelled through Europe with crosses to appease God and repel the Plague, blamed the Jewish for the Plague.
What event ended the Great Plague of London?
The Great Fire of London.
Influenza Virus
The virus that causes the flu, a contagious respiratory illness characterized by symptoms such as fever, cough, and body aches.
Plague Doctors
Hired to determine if an individual was infected with the Plague, wore a cloak, mask, and carried a poking stick.
Plague Doctor Treatments
Water and vinegar
Lancing bubos
Crushed emeralds
Bleeding
“sweating out the disease beside a fire
Pest Houses
Used during the Plague epidemic to contain the disease, the starting of public health efforts to contain and treat disease.
When was the Great Fire of London?
September 1666.
Influenza
A viral infection that enters through the nose and settles in the respiratory tract.
Flu Symptoms
Headache
Fever,
Body aches and chills
Extreme tiredness,
Joint aches
Runny/stuffy nose
Sore throat
Coughing
Vomiting.
What symptom mainly differentiates the Flu from the common Cold?
Vomiting.
Incubation period of the Flu
1-4 days, average of 2.
Influenza Virus Structure
Lipid envelope with hemagglutinin and neuraminidase proteins.
Type A Influenza
Most virulent type found in birds, pigs, and humans. The source of all major pandemics.
Type B Influenza
Found almost exclusively in humans and causes mild symptoms.
Type C Influenza
Found in pigs and humans and causes mild symptoms.
Function of Hemagglutinin
Allows the Flu virus to bind the host cell.
Function of Neuraminidase
Allows the Flu virus to be released from the host cell.
Antigenic drift
Small mutations in hemagglutinin and neuraminidase proteins that produce similar viruses.
Viral Recombination
New strain created when different viral sources mix within a host.
Influenza A subtypes
H1N1, H2N2, H3N2, H5N1.
Neuraminidase inhibition
Antiviral flu drugs like Oseltamivir and Zanamivir that prevent virus release from host cells.
Explain the nomenclature of Influenza viruses
Antigenic type first (A, B, C)
Host of origin (Swine, Chicken, Human = no designation)
Geographical origin (California, Hong Kong)
Subtype (H1N1, H3N2)
How are vaccines manufactured?
3 strains are selected, inoculated individually in fertilized chicken eggs, and combined to make a vaccine.
Seasonal Influenza Vaccine
Global surveillance system determines strains for the yearly vaccine.
Flu Vaccine Types
Shot (inactivated virus) and nasal spray (live attenuated virus).
