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54 Cards in this Set
- Front
- Back
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Mortality and Morbidity Rates |
Mortality Rate: - the total number of deaths in a population due to a certain disease
- often expressed as percentage
- ex: ebola currently between 50-90% (depends on location and availability of response) |
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Mortality and Morbidity Rates |
Morbidity Rate: number of people afflicted with a certain disease |
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Frequency of Disease |
Incidence: the number of new cases of a disease occurring during a specific period of time
- ex: flu: peak season from Dec-March (look at number of new cases confirmed by lab between this time) |
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Frequency of Disease |
Prevalence: the total cumulative number of cases of a disease in a certain area and time period
- defined area is key* |
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Frequency of Disease |
Sporadic: disease which exhibits new cases at irregular intervals in unpredictable geographic regions
- ex: anthrax (don't anticipate these cases; unpredictable - used most commonly in biological warfare) |
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Frequency of Disease |
Endemic: A native disease that prevails continuously in a geographic region
- ex: malaria, common cold
- ebola: found in West Africa - not something we would expect here |
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Frequency of Disease |
Epidemic: a sudden and simultaneous outbreak or increase in the number of cases of disease in a community |
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Frequency of Disease |
Types of Epidemics Propagating: small # of people ill initially, then disease is passed on to increasingly large numbers (exponential rise in cases)
Common Source Outbreak: occurs when there is a sharp rise in the # of cases, then a decline (ex: food poisoning) |
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Frequency of Disease |
Pandemic: a disease afflicting an increased proportion of the population over a wide geographic region - often worldwide - ex: cholera pandemic, H1N1 pandemic; strains of different diseases that we have no immunity against |
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Transmission of Microorganisms |
Communicable disease: infection capable of being transmitted from one individual to another
Can spread from: - person to person - person to animal - animal to person |
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Transmission of Microorganisms |
Non-communicable disease: an infectious disease that does not arrise through the transmission of an infectious agent from host to host
Primarily occurs when an immune-compromised - opportunistic |
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Transmission of Microorganisms |
Non-communicable disease con't
Accidental contact with a facultative parasite that exists in a non-living reservoir - parasites that can survive on inanimate surfaces for longer than normal; - transmits easier when immune- compromised person comes into contact |
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Transmission of Microorganisms |
Contagious disease: transmitted by direct contact with infected people and their fresh secretions or excretions - can be spread quickly and easily in not contained - one of biggest assets is hand hygiene followed by PPE |
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Portals of Entry |
Skin - Pathogens use break in integrity of skin as
- Some infectious agents create their own passageways using digestive enzymes (ex:worms) |
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Portals of Entry |
Skin - Some infectious agents enter through bites (ex:Rickettsiae)
- Artificial means for breaching the skin = hypodermic needles (ex: Hepatitis, AIDS, tetanus) |
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Portals of Entry |
G.I. Tract - Portal of entry for pathogens contained in food, drink and other ingested substances
- Adapts to survive digestive enzymes and abrupt changes in pH
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Portals of Entry |
G.I. Tract - Bacterial pathogens that localize in the mucosa of the small or large intestines (ex: Salmonella, Shigella, Vibrio, E. coli)
- Viruses that enter through the gut |
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Portals of Entry |
Respiratory - Microbes can be transferred from one site to another because of continuous mucous membrane
- Enables travel from upper to lower respiratory system into areas that should be sterile |
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Portals of Entry |
Respiratory - Oral, nasal, auditory, trachea act as gateways
- Size determines how far pathogen can be carried into the respiratory tree - the smaller the pathogen, the more likely it is to cause infection due to lack of removal mechanism at deep levels of bronchi |
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Portals of Entry |
Respiratory Inhalation of pathogens into lower respiratory regions can result in pneumonia - Streptococcus pneumoniae severe pheumoniae) |
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Portals of Entry |
Urogenital - Pathogens are contracted by sexual means
- Microbes enter skin or mucosa of the penis, external genitalia, vagina, cervix and urethra |
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Portals of Entry |
Urogenital - Some can penetrate unbroken surface; others require a cut or abrasion
- Not all urogenital diseases are STI’s
- Displaced microbiota or opportunistic overgrowth of normal flora |
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Portals of Entry |
Pregnancy and Birth - Some microbes can cross the placenta and enter the umbilical vein
- Spread by fetal circulation into fetal tissues
- Some infections occur peri-natally: baby |
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Portals of Entry |
Pregnancy and Birth - Syphilis - Toxoplasmosis - Other diseases (hep B, ADIS, Chlamydia) - Rubella - Cytomegalovirus (dont see a lot of but when do, they are usally very sick) - Herpes simplex virus |
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Reservoirs |
Reservoir: primary habitat in the natural world from which a pathogen originates reservoirs
Source: individual or object from which an infection is actually acquired |
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Reservoirs |
- Reservoir and source can be the same - ex: syphilis - reservoir and source is the human body
- Reservoir and source can be different - ex: Hepatitis A - reservoir = human carrier - source = contaminated food |
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Reservoirs |
Exogenous: originating from a source outside of the body (environment, another host)
Endogenous (autogenous): already existing on or in the body - ex: resident flora - translocates deeper than where supposed to be - ex: latent infection - shingles |
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Reservoirs |
Non-Living Reservoirs - Some can thrive in soil, water and air
- Most are saprobes and benefit humans
- Some are opportunistic
- A few are true pathogens |
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Reservoirs |
Non-Living Reservoirs - Soil can harbour both vegetative and resistant forms of pathogens
- Pathogenic fungi spread by spores in soil/dust
- Water supports less pathogens as it carries fewer nutrients |
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Methods of Disease Transmission |
- Contact Transmission - Direct Contact - Indirect Contact
- Vehicle Transmission
- Vector Transmission |
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Methods of Disease Transmission (Contact) |
Direct Contact: direct physical contact of the infectious agent between hosts without an intermediate object
- Most obligate intracellular parasites too sensitive to survive outside of a host ∴ can only be transmitted through direct contact |
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Methods of Disease Transmission (Contact) |
Indirect Contact: transmission that occurs when the pathogen is transmitted from the reservoir to the susceptible host by an intermediary
- fomite (non-living object)
- droplets |
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Methods of Disease Transmission (Contact) |
Droplet Transmission: particles >5 um in size are heavy enough to fall to environmental surfaces
- do not stay suspended in air currents, travel less than one metre |
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Methods of Disease Transmission (Contact) |
Droplet Transmission Released through: - exhaling - laughing - coughing - sneezing |
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Methods of Disease Transmission (Vehicle) |
Vehicle Transmission
Help transmit from one patient to another
- airborn - foodborn - waterborn - bodily fluids |
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Methods of Disease Transmission (Vehicle) |
Vehicle Transmission
Vehicle: any inanimate material commonly used by humans that can transmit infectious agents
Common vehicle: a single material that serves as the source of infection for many individuals (ex: e. coli outbreak from water in Walkerton) |
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Methods of Disease Transmission (Vehicle) |
Airborne Transmission: Indoor air can serve as a medium for the suspension and dispersal of certain respiratory pathogens
- Pathogens spread by droplet nuclei, other aerosols and dust that travel for more than 2 metres from the reservoir to the host |
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Methods of Disease Transmission (Vehicle) |
Airborne Transmission
Droplet nuclei: dried residue of fine droplets produced by mucus and saliva sprayed while sneezing and coughing; mildly produced during vocalization
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Methods of Disease Transmission (Vehicle) |
- < 5 µm in diameter - Large enough to bear a single bacterium, small enough to stay airborne
- Travel deep into respiratory tree
- ex: TB, Chickenpox, Measles |
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Methods of Disease Transmission (Vehicle) |
Food as a vehicle
- Source of infectious agent can be: - soil - food handler - mechanical vector |
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Methods of Disease Transmission (Vehicle) |
Food as a vehicle Oral-fecal route – fecal carrier contaminates food
- ex: hepatitis A, typhoid fever |
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Methods of Disease Transmission (Vehicle) |
Waterborne transmission: occurs through untreated or poorly treated sewage
- ex: E. coli, cholera, amebic dysentery |
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Methods of Disease Transmission (Vehicle) |
Bodily fluid transmission: pathogens spread through urine, blood, sputum, etc.
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Methods of Disease Transmission (Vector) |
Vector Transmission: an animal, usually an arthropod, transfers an infectious agent from one host to another
Classifications: - biological vector - mechanical vector |
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Methods of Disease Transmission (Vector) |
Biological vector: transmits infectious agent by biting, aerosol formation or touch
Biting vectors: - injecting infected saliva into the blood (mosquitos) - defecate around bite wound (flea) - regurgitate blood into the wound (tsetse fly) |
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Methods of Disease Transmission (Vector) |
Biological vector
**Actively participates in the pathogen’s life cycle (host)**
- pathogen could not survive without host |
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Methods of Disease Transmission (Vector) |
Mechanical vector: organisms transferred on body or feet of vector (ex: house fly)
- not necessary to the life cycle of an infectious agent
- vector transports pathogen without becoming infected |
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Zoonosis |
Zoonosis: an infection indigenous to animals but naturally transmissible to humans
- Human is a dead-end host; does not contribute to the natural persistence of the microbe
- Impossible to completely eradicate without destroying animal reservoir |
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Zoonosis |
Sentinel animals: usually domestic animals (horses or chickens) used for surveillance
- placed at various sites throughout a community
– indicates exposure to a pathogen |
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Horizontal vs. Vertical Transmission |
Horizontal: person to person transmission
- one body site to another on the same person
Vertical: parent to offspring, transmitted in utero |
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Human Carriers |
Human Carriers: individuals who harbour specific organisms of a disease
- Capable of transmitting disease whether or not showing signs and symptoms
- Duration of carrier state can be short- or long-term (classified based on duration) |
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Human Carriers |
Chronic Carrier: carrier state continues after recovery
Asymptomatic Carrier: - no signs or symptoms of disease - microbes carried as commensals - also called a healthy carrier - very difficult to discover/control |
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Human Carriers |
Passive/transient carrier: individual carries organisms for a short time
- AKA transient carrier
- A problem with health care workers (pass onto patients with compromised immune systems) |
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Human Carriers |
- Strategies to reduce passive transmission: - proper hand washing; PPE - proper handling of contaminated materials - aseptic techniques |
