Module 2 - Infectious Diseases Flashcards
Impacts of Infectious Diseases in history:
✘ 14th century: Europe - plague kills 20-45% of the world’s population
✘ 1831: Cairo - 13% of population succumbs to cholera
✘ 1854-56: Crimean war – deaths due to dysentery were 10 times higher than deaths due to casualties
✘ 1899-1902: Boer War – deaths due to dysentery were 5 times higher than deaths due to casualties
What is an Infectious (Communicable) Disease?
“An illness due to a specific infectious agent or its toxic products that arises through transmission of that agent or its products from an infected person, animal, or reservoir to a susceptible host, either directly or indirectly through an intermediate plant or animal host, vector, or the inanimate environment.”
What is the Epidemiologic Triangle? What make it up?
One of the longstanding models used to describe the etiology of infectious diseases
Includes three major factors: agent, host, and environment
- Agent: the cause of a disease
- Host: an organism, usually an animal or human, that harbors disease
- Environment: The domain in which disease-causing agents may exist, survive, or originate
Examples of disease agents:
Toxin, Parasitic Disease, and Zoonosis
Define toxin (agent) and give examples.
✘ Some infectious disease agents, instead of acting directly, produce a toxin that causes illness.
✘ A toxin usually refers to a toxic substance made by living organisms.
• Examples of illness: foodborne intoxications such as botulism
What is Parasitic Disease (agent) and give examples?
✘ An infection caused by a parasite, which “…is an organism that lives on or in a host organism and gets its food from or at the expense of its host.”
✘ Example: amebiasis
What is zoonosis (agent)?
“An infection or infectious agent transmissible under natural conditions from vertebrate animals to humans.”
What are host characteristics?
Immunity is the host’s ability to resist infection by the agent (You’ll hear more about this in Unit 10).
Other factors related to host responses:
• Incubation period • Subclinical illness • Generation time • Carrier status
How can infectious disease agents be transmitted?
✘ Direct transmission - (Person to person) ✘ Indirect transmission - Vehicle-borne infections - Airborne infections - Vector-borne infections
What is the Portal of Exit)?
✘ For an infected person, a portal of exit is the site from which the agent leaves that person’s body.
✘ Examples: • Respiratory passages • Alimentary canal • Genitourinary system • Skin lesions
What is the Portal of Entry?
Site where the agent enters the body, such as, a skin wound
Define direct transmission:
“Direct and essentially immediate transfer of infectious agents to a receptive portal of entry through which human or animal infection may take place….”
Define indirect transmission:
Involves intermediary sources of infection such as vehicles, droplet nuclei (particles), and vectors.
Define vehicle-borne infections:
These infections result from contact with vehicles, which are contaminated, nonmoving objects.
Examples: • Fomites • Unsanitary food • Impure water
What is a Fomite?
An inanimate object that carries infectious disease agents
Examples: • Classroom door-knob • Discarded tissues
What are Airborne infections?
Involve the spread of droplet nuclei (particles) that are present in the air.
Example: infections caused by stirring up dust that carries fungi or microbes
What are Vector-borne infections? Examples?
Transmission of an infectious disease agent may happen when the vector feeds on a susceptible host.
Examples include: • Bacterial diseases • Lyme disease (tick) • Arthropod-borne (arboviral) diseases • Eastern equine encephalitis (mosquito) • Parasitic diseases • Malaria (mosquito)
Examples of Significant Infectious Diseases:
✘ Sexually transmitted diseases ✘ Foodborne diseases ✘ Waterborne diseases ✘ Vector-borne diseases ✘ Vaccine-preventable diseases ✘ Zoonotic diseases ✘ Emerging infections ✘ Bioterrorism-related diseases
What is a vector?
A vector is an animate, living insect or animal that is involved with the transmission of disease agents.
What are zoonotic diseases? Examples?
✘ Diseases transmitted from vertebrate animals to human beings.
✘ Examples: • Rabies • Anthrax • Avian influenza • Hantavirus pulmonary syndrome • Toxoplasmosis • Tularemia (rabbit fever)
What are Foodborne illnesses? Examples?
✘ Biologic agents of foodborne illness include bacteria, parasites, viruses, and prions (linked to mad cow disease).
✘ Examples of bacterial agents include: • Campylobacter • Clostridium botulinum • Salmonella
What is infectivity?
The capacity of an agent to enter and multiply in a susceptible host and thus produce infection or disease.
What is Virulence?
Refers to the severity of the disease produced, i.e., whether the disease has severe clinical manifestations or is fatal in a large number of cases.
Why do infectious diseases still remain a threat?
- New types of diseases are constantly evolving and imperiling public health.
- Outbreaks caused by bioterrorism are a potential threat.
- Some infectious disease agents mutate into forms that resist conventional antibiotic treatment.
