Infectious Diseases Overview

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Questions and Answers

What defines an infectious disease?

Microorganisms that utilize a host's resources to reproduce. (correct)

Microorganisms that reproduce without a host.

Microorganisms that exist in a dormant state within the host.

Microorganisms that enhance the host's immune response.

Which of the following statements about microorganisms is correct?

All microorganisms cause disease.

Microorganisms can only reproduce inside the host.

Microorganisms are only harmful during specific seasons.

Most microorganisms are harmless and do not cause disease. (correct)

Which element is essential for defining the term 'host' in the context of infectious disease?

It must exclusively eliminate pathogens.

It must provide resources for pathogen reproduction. (correct)

It must be a microorganism.

It must exist in a stable environment.

What is the significance of Koch’s postulates in the study of infectious diseases?

They provide a framework for identifying the causative agents of infectious diseases. Signup and view all the answers

What aspect of infectious disease transmission is crucial to understand?

Various methods exist for the transmission of infectious diseases. Signup and view all the answers

Which age group is most likely to be affected by infectious diseases?

Infants Signup and view all the answers

What is a primary reason for the decrease in mortality rates over time?

Increased sanitation Signup and view all the answers

Which of the following is NOT considered a major group of pathogens that infect humans?

Nutrients Signup and view all the answers

What is the primary goal of 'flattening the curve' during an epidemic?

To slow the spread of infection to manage healthcare resources Signup and view all the answers

In which type of country are individuals more likely to die from infectious diseases rather than chronic diseases?

Lower-middle income countries Signup and view all the answers

What happens to the immune system as age increases?

It becomes weaker Signup and view all the answers

Why do new diseases, such as zoonotic diseases, continue to emerge?

Pathogens reproduce more quickly than hosts, leading to evolution Signup and view all the answers

What does the term 'virulence' refer to in the context of infectious diseases?

The severity of a disease caused by a pathogen Signup and view all the answers

What does the 'epidemic curve' indicate in terms of public health?

The pattern of infection incidence over a specific time frame Signup and view all the answers

What is a reason that the immune system may not fully develop in certain environments?

Living in a low resource environment Signup and view all the answers

What is a defining characteristic of prions?

They are infectious proteins. Signup and view all the answers

Which disease is associated with prion infection in humans?

Kuru Signup and view all the answers

What is the primary mode of transmission for vector-borne diseases?

Through intermediary species such as insects Signup and view all the answers

Which factor is associated with increased virulence in pathogens according to evolutionary theory?

Use of disease vectors for transmission Signup and view all the answers

What is a common transmission method for respiratory pathogens?

Droplet transmission Signup and view all the answers

Which of the following diseases is NOT caused by prions?

Tuberculosis Signup and view all the answers

What role does the skin play in pathogen transmission?

It is a common entry point due to thin epithelial tissues. Signup and view all the answers

What is a significant requirement for a pathogen to evolve to lower virulence?

Creating conditions through disrupted transmission modes Signup and view all the answers

Which of the following is NOT one of Koch's postulates?

The pathogen must have a known vector Signup and view all the answers

Which type of organism is characterized by lacking a nucleus and reproducing by duplicating DNA?

Bacteria Signup and view all the answers

What characteristic is unique to viruses compared to other infectious agents?

They cannot complete their life cycle without a host Signup and view all the answers

Which statement about fungi is INCORRECT?

Most fungi are harmful to humans Signup and view all the answers

Which group of pathogens includes multicellular organisms that can cause disease in humans?

Helminths Signup and view all the answers

Which of the following statements about protozoa is true?

They can easily evade the host's immune defenses Signup and view all the answers

The majority of viral infections depend on which of the following host characteristics?

The receptor proteins on host cells Signup and view all the answers

How do helminths typically damage their hosts?

By feeding on host tissues and nutrients Signup and view all the answers

Study Notes

Course Information

Course: Anthropology 243, Medical Anthropology: Human Biology and Health
Course year: Fall 2024
Textbook: Medical Anthropology: A Biocultural Approach, 4th Edition, by Andrea S. Wiley and John S. Allen

Announcements

Exam 2 grades will be posted by Thursday.
Exam 3 is Tuesday, December 10th, 8:00 AM – 9:00 AM in LH 8 (60 minutes).
Students with more than two exams within a 24-hour period can request a makeup exam. The professor teaching the largest section of the course will arrange the makeup.

Schedule

Schedule up to Thanksgiving Break.
Tuesday, November 12th: Introduction to Infectious Diseases (Chapter 8).
Thursday, November 14th: Guest lecture by Meg Gauck on Colonialism and Tuberculosis.
Tuesday, November 19th: The Immune System.
Thursday, November 21st: Film Discussion: Bending the Arc.
Tuesday, November 26th: No class (Friday classes meet).
Thursday, November 28th: No class (Thanksgiving Break).

Infectious Disease I (Wiley & Allen Ch. 8)

Textbook chapter: Wiley and Allen, Chapter 8: 240-248
What is infectious disease?
Epidemiology
Germ theory and Koch's postulates
Types of infectious diseases
Infectious disease transmission

What is an Infectious Disease?

Microorganisms use hosts' resources for reproduction, disrupting the immune response or physiology.
Host: the organism the infection targets.
Most microorganisms don't cause disease. Pathogens (germs) do.
Six major pathogen groups that infect humans: viruses, bacteria, protozoa, fungi, helminths, and prions.
Exposure and susceptibility vary.

Deaths from Major Infectious Diseases

Data showing declines in deaths from infectious diseases over time, correlating with the introduction of vaccines and treatments.
Life expectancy has increased significantly.

Top 10 Causes of Death Globally (2021)

Leading causes in 2021: Ischemic heart disease, COVID-19, Stroke, Chronic Obstructive Pulmonary Disease, Lower Respiratory Infections, Trachea, Bronchus, Lung Cancers, Alzheimer's disease and other dementias, Diabetes Mellitus, Kidney Diseases, and Tuberculosis.
Differences in mortality rates exist based on the income level of the country (more infections among low/middle income).

Low-Income Countries Death Causes (2021)

Leading causes: Lower respiratory infections, Stroke, Ischemic heart disease, Malaria, Preterm Birth Complications, COVID-19, Diarrhoeal diseases, Tuberculosis, Birth asphyxia and birth trauma, and HIV/AIDS.

Lower-Middle Income Countries Death Causes (2021)

Leading causes: COVID-19, Ischaemic heart disease, Stroke, Chronic obstructive pulmonary disease, Lower respiratory infections, Tuberculosis, Diarrheal diseases, Diabetes mellitus, Cirrhosis of the liver, and Preterm birth complications.

High-Income Countries Death Causes (2021)

Similar to global trends, but with chronic diseases like heart disease and cancer being the leading causes.

What Age Group is Most Affected?

Causes of death for children under five: Prematurity, Acute respiratory infections, Birth asphyxia and birth trauma, Congenital anomalies, Diarrhoea, Neonatal sepsis, Injuries, Malaria, Meningitis/encephalitis, Measles, HIV/AIDS, and Tetanus.

Top 10 Causes of Death in the US (2023)

Leading causes in US 2023: Heart disease, cancer, unintentional injury, stroke, chronic lower respiratory diseases, Alzheimer's disease, diabetes, kidney disease, chronic liver disease and cirrhosis, and COVID-19.

Epidemic Curve

Epidemic: a rise in the incidence of a disease in a population.

Flattening the Curve

Healthcare systems must accommodate capacity to handle spreading infections. Slowing the rate of spreading is key.

Why Do We Still Have Infectious Diseases?

Conflicts between pathogens and hosts.
Pathogen vs. human evolution (pathogens reproduce faster).
Novel environments—like antibiotic resistance.

New Diseases

Zoonotic diseases: transferred from animals to humans.

Changes in Virulence

Virulence: severity of a disease caused by a pathogen.

How do we know that a set of symptoms result from an infection?

Koch's Postulates are the criteria we use to determine if a disease is infectious.

Classes of Infectious Disease

Viruses, Bacteria, Protozoa, Fungi, Helminths, and Prions

Viruses

DNA or RNA surrounded by protein.
Obligate parasites that can't complete their life cycle without a host.
Mimic host cell proteins to gain entry.
Hosts are carriers of the infections.

Bacteria

Single-celled prokaryotes (no nucleus)
Reproduce by duplicating their DNA and dividing.
Over 400 genera; 40 known to cause human disease.
10x the number of bacterial cells compared to human cells.
Significant diversity in survivability outside the host
Variety in form (spores, flagella, pili)
Able to survive in a variety of environments (aerobic, anaerobic)

Protozoa

Single-celled eukaryotes with a nucleus.
Able to evade host immune systems.
Infections are difficult to treat; cellular structures similar to the host.
Variability in reproduction and growth stages (different organs, intermediate species, vector transmission).
Vector= agent that carries and transmits pathogen.

Fungi

Eukaryotes with a nucleus.
70,000 species; few harmful to humans.
Low virulence unless the host is immunocompromised.
Highly variable (yeasts, spores).

Helminths (Worms)

Multicellular organisms
3 types cause human disease (roundworms, tapeworms, flukes).
50% of global population is infected today (historic high).
Difficult to treat (tough outer coatings).
Transmission through intermediate hosts (water, soil, food).

Prions

Infectious proteins, rather than DNA/RNA
Unknown replication mechanism.
Transmissible spongiform encephalopathies (TSEs), a group of neurodegenerative diseases.
Human (Creutzfeldt-Jakob disease, Kuru)
Animal (Bovine spongiform encephalopathy, Scrapie).
Transmission can be through exposure to infected brain tissue or spinal fluid

How are Pathogens Spread?

Direct transmission (contact).
Droplet transmission (less than 1 meter).
Vector-borne (insects, animals, contaminated objects).

Evolution of Virulence

Factors affecting pathogen virulence:
Intermediate disease vectors
Transmission (mobile host vs non-mobile host)
Casual human-to-human transmission

Next Time

Guest lecture from Meg Gauck.
Attendance and participation required.

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Description

Test your knowledge on infectious diseases with this quiz covering key concepts such as microorganisms, Koch's postulates, and transmission dynamics. Understand the significance of age and environment in disease susceptibility, and explore what defines a host and virulence. This quiz is a great review for anyone studying public health or microbiology.