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Questions and Answers
What is an example of a vehicle transmission disease?
What is an example of a vehicle transmission disease?
Iatrogenic infections are always caused by airborne pathogens.
Iatrogenic infections are always caused by airborne pathogens.
False
What is Staphylococcus aureus commonly associated with?
What is Staphylococcus aureus commonly associated with?
Nosocomial infections
The process by which a pathogen escapes the host's immune system is known as ______.
The process by which a pathogen escapes the host's immune system is known as ______.
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Match the transmission mechanisms with their definitions:
Match the transmission mechanisms with their definitions:
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Which of the following pathogens is transmitted by mosquitos?
Which of the following pathogens is transmitted by mosquitos?
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Virulence factors include characteristics that allow pathogens to cause infection.
Virulence factors include characteristics that allow pathogens to cause infection.
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What are the examples of vector transmission?
What are the examples of vector transmission?
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What is the primary mode of transmission for diseases like chicken pox and influenza?
What is the primary mode of transmission for diseases like chicken pox and influenza?
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Fomites are living organisms that contribute to the spread of infectious diseases.
Fomites are living organisms that contribute to the spread of infectious diseases.
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What term describes the transfer of infection from an infected parent to their offspring during childbirth?
What term describes the transfer of infection from an infected parent to their offspring during childbirth?
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The entry points where pathogens enter the body are referred to as __________.
The entry points where pathogens enter the body are referred to as __________.
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Match the following types of contact transmission with their definitions:
Match the following types of contact transmission with their definitions:
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What is the definition of pathogenicity?
What is the definition of pathogenicity?
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Virulence indicates the ability of a pathogen to cause disease.
Virulence indicates the ability of a pathogen to cause disease.
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Name an example of a pathogen with high virulence.
Name an example of a pathogen with high virulence.
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The type of disease that cannot be transmitted from person to person is called a __________ disease.
The type of disease that cannot be transmitted from person to person is called a __________ disease.
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Which of the following is an example of an infectious agent?
Which of the following is an example of an infectious agent?
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An asymptomatic carrier shows visible signs of infection.
An asymptomatic carrier shows visible signs of infection.
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Match the following types of carriers with their definitions:
Match the following types of carriers with their definitions:
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Which organism can act as a reservoir for rabies?
Which organism can act as a reservoir for rabies?
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What is the role of a reservoir in disease transmission?
What is the role of a reservoir in disease transmission?
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Transmission from animal to human is known as __________.
Transmission from animal to human is known as __________.
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Study Notes
University of Doha for Science & Technology
- College of General Education
Microorganisms and Disease: Disease Processes
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Infectious diseases are caused by organisms that spread from person to person.
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Communicable diseases can spread from person to person.
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Infectious diseases can spread through ingestion, bites, coughs.
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Non-Infectious diseases are not caused by a disease.
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Non-communicable diseases aren't spread.
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They can be caused by genetics, the environment, lifestyle or nutritional issues.
Microorganisms and Disease
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Infectious agents can be viruses, bacteria, protozoans, fungi, and worms.
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The infection process occurs in stages:
- Exposure
- Establish focus of infection
- Colonization and overcoming host defenses
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Surfaces for infection can be skin, gastrointestinal, respiratory, or urogenital tracts.
Human Infectious Diseases
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Bacteria are responsible for various diseases. Examples include Tuberculosis, Pneumonia streptococcal infections, Gonorrhea, Scarlet Fever, Tetanus, Diphtheria, Pertussis, and Bubonic Plague.
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Viruses cause various diseases. Examples include AIDS/HIV, Influenza, Herpes, Hepatitis, Common Cold, Poliomyelitis, Measles, Mumps, and Rubella, Infectious mononucleosis.
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Fungi cause diseases such as Candidiasis, Athlete's foot, Jock itch, Nail fungus, and Ringworm.
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Protozoa cause diseases such as Amebiasis, Amebic meningoencephalitis, Malaria, Trichomoniasis, Toxoplasmosis, Giardiasis, Balantidiasis, Cryptosporidiosis, and Pneumocystosis.
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Helminthes/Parasites include Trichuriasis, Hookworm, Lympathic filariasis, Schistosomiasis, and Ascariasis.
Pathogenicity
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Pathogenicity is the ability of a pathogen to cause disease.
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Some pathogens more easily cause disease than others.
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High pathogenicity examples include Yersinia pestis, Listeria species, and Clostridium tetani.
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Low pathogenicity examples include Staphylococcus aureus.
Virulence
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Virulence is the severity of illness caused by a pathogen.
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All pathogens cause some level of disease.
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High virulence pathogens cause severe illness.
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Low virulence pathogens cause less severe illness.
Examples of Illness caused by different virulence levels
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Common colds generally cause less severe illness.
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H5N1 influenza can cause severe symptoms like pneumonia and multi-organ failure and is more virulent than common influenza.
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COVID-19 and Influenza share similar symptoms:
- Both start 1-4 days or 1-14 days after exposure.
- Both have varying degrees of severity.
Sources of Infection: Reservoirs
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Reservoirs are sources of infection where a pathogen can survive until it's passed to a host.
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Can be a living or non-living object.
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Infected humans are a reservoir from consumption of infected food or through transmission of viruses and bacteria.
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Animals can be reservoirs such as monkeys for malaria, cats for diseases, dogs for many diseases (including rabies), and various wildlife.
Human Carriers - Classifications
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A passive carrier never shows outward signs of disease.
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An incubatory carrier can transmit pathogens during the incubation period. Examples include measles, mumps, and polio.
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A convalescent carrier transmits disease while recovering. Examples include cholera, typhoid fever, and diphtheria.
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An active carrier has recovered but can still transmit disease indefinitely.
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Tyhpoid Mary is an example of an asymptomatic carrier.
Non-Living Reservoirs
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Soil can harbor bacteria like Clostridium leading to conditions like tetanus and gangrene.
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Water can harbor Vibrio cholera which causes extreme diarrhea and dehydration.
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Airborne pathogens (e.g., anthrax, chickenpox, influenza, measles, and TB).
Portals of Entry/Exit
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Pathogens need entry portals (e.g., eyes, ears, cuts, abrasions, mouth) to cause infection within the host.
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Disease exit portals (e.g., eyes, ears, mouth, anus, blood) when infectious agents leave the host.
Modes of Transmission
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Transmission of diseases occurs when a reservoir spreads infection.
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This happens from a portal of exit to another organism.
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There are three transmission modes: contact, vehicle, and vector.
Disease Transmission
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There are horizontal and vertical transmission modes.
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Horizontal transmission includes human-to-human, animal-to-human, and sexual contact.
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Vertical transmission includes diseases acquired from mother to fetus like syphilis or gonorrhea, congenital conjunctivitis.
Contact Transmission
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Contact spread occurs when an infectious disease transmits from an infected individual to a new host.
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This transmission can be direct, indirect, or droplet.
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Direct contact is from body contact. Examples include shaking hands, kissing, or sexual contact.
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Indirect contact is from a contact with non-living objects (e.g., doorknobs, fomites).
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Droplet spread is from respiratory droplets released by an infected individual.
Vehicle Transmission
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Vehicle transmission occurs when a non-living object spreads infection.
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Examples include waterborne (cholera), airborne (flu), and foodborne (salmonella).
Vector Transmission
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Vector transmission involves a living organism (vector) that carries pathogens from a reservoir to a host.
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Examples include mosquitoes (malaria), fleas (bubonic plague), lice, flies (African Sleeping Sickness).
Nosocomial Transmission
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Nosocomial infections are infections acquired in healthcare facilities. These can be secondary to a pre-existing condition or occur shortly after admission/within 14 days of discharge.
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Iatrogenic infections result from medical procedures, surgeries or healthcare staff.
Bacteria causing Nosocomial Infections
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Staphylococcus aureus (frequently resistant to antibiotics, like MRSA) is a common example.
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Other examples include Escherichia coli, Enterococci, and Candida. Infectious microorganisms are often found on skin and mucous membranes.
How Do Bacteria Cause Disease?
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Virulence factors are structural/physiological characteristics of bacteria that allow them to cause infection.
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Adherence characteristics of microbes allow bacteria to stick to host cells, a key initial step to infection.
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Evasion helps pathogens escape the host's immune defenses.
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Toxins damage host cells/tissues.
Bacterial Adherence & Infection
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Adhesins are molecules bacteria use to attach to host cells.
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Capsules, pili/fimbriae are examples of adherence factors that contribute to bacterial attachment and infection.
Invasiveness/Evasion Mechanisms
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Invasiveness helps bacteria spread through tissues (e.g., hyaluronidase enzyme).
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Evasiveness mechanisms allow bacteria to avoid immune responses (e.g., coagulase enzyme, streptokinase enzyme).
Bacterial Toxins
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Endotoxins are part of the cell wall; release causes fever, shock.
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Exotoxins are secreted proteins; cause more potent, damaging effects (hemolysins, leukocidins, responsible for diseases like botulism, tetanus, cholera).
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Description
Explore the intricate processes involved in infectious and non-infectious diseases. This quiz covers the characteristics of microorganisms, the stages of infection, and the differences between communicable and non-communicable diseases. Test your knowledge of how diseases spread and affect humans.
