Module 2 Flashcards
Pathogens
Disease causing organisms
Pathogenesis
The development of disease
Infective disease
A pathogen capable of entering, multiplying, and surviving in a susceptible host
Virulence
The severity of the disease; extent of pathogenicity
Invasiveness
The ability of a pathogen to enter and grow in a susceptible host
Communicability
Ability to be spread
Etiology
The study of the causes of disease
Infectious disease
Caused by a microbial agent
Communicable disease
Infectious disease who is agent is transmissible from an infected person, animal, or in inanimate source to a susceptible host
**not all infectious diseases are communicable
Disease categories
Acute: severe, short, treatable, recovery or death
Subacute: intermediate in duration and severity, may result in recovery
Chronic: less severe, long duration, may not result in recovery
Infectious agents
Viruses Bacteria Prions Metazoa Protozoa Fungus Rickettsia
Examples of environmental factors
Temperature Humidity Altitude Radiation Food/drink Neighborhood Housing Pollution
Examples of host factors
Age Race/ethnicity Sex Genetics Lifestyle (diet/exercise) Smoking Immune status/vaccination Previous illness Occupation Comorbidities
Examples of bacterial agents
Methicillin Resistant Staph Aureus Group A Strep Legionella Salmonella Mycobacterium tuberculosis Listeria
Viruses
Infectious agent that requires host for replication Examples: Influenza Hepatitis Varicella Measles Mumps Most vaccine preventable disease
Fungal diseases (mycoses)
Opportunistic, infect immunocompromised patients
Examples:
Candida
Aspergillus
Prions
Abnormal infectious proteins
Examples:
-Animals: mad cow, scrapie
-Humans: Creutzfeldt-Jakob disease, kuru
*Cause transmissible spongiform encephalopathies (TSEs)
**Prions are highly resistant to traditional sterilization methods
Host factors
The degree and severity of infection depends on the host’s ability to fight the infectious agent
Host
A person or animal in which an infectious agent lives
Defense mechanisms (of the host)
Nonspecific: skin, mucosal surfaces, tears, saliva, gastric juices, the immune system
Disease specific: immunity against an agent
- Active: immunization or prior infection
- passive: maternal antibodies, Immunoglobulin
Environment
The domain external to the host in which the infectious agent may exist, survive, or originate
- affects the survival of the agent
- brings the agent and the host into contact
The chain of infection
Infectious agent Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host
Reservoir
Where an infectious agent normally lives and multiplies
Vector
Living nonhuman carrier of disease
Ex: mosquito
Fomite
Articles that transmit infection
Ex: doorknob
Carrier
A person who spreads an infectious agent
- Harbors organism
- Not infected
Modes of transmission
Direct: contact kissing, sexual activity, in utero, via breastmilk, airborne droplets, droplet nuclei
Indirect:
- animate: human carrier
- animate: insect or animal vector
- inanimate: free living organisms and the environment, water, sewage, dust, fomite, etc.
Portals of entry
Conjunctiva of eye Mouth GI tract Respiratory tract Reproductive tract Urinary tract Cardiovascular system Skin breaks Percutaneous (trauma, injection) Transplacental Organ transplants
Communicable disease categories
Food-borne Arthropod-borne Mycoses Emerging Vaccine preventable Zoonotic Waterborne
Food-borne diseases
Significant issue for institutional/residential health care settings
Ex: E. coli, salmonella, Norovirus, listeria
Waterborne diseases
Contaminated water delivery systems have potential for disease transmission
Ex: legionella
Arthropod-borne diseases
Blood-feeding arthropod (insect) vectors transmit disease agents to vertebrate hosts
Vector examples: mosquitoes, tics, flies
Disease examples: malaria, encephalitis
Zoonotic diseases
Can be spread from vertebrate animals to humans under natural conditions
Ex: West Nile virus, avian influenza, rabies
HC management implications:
- pet therapy
- pest exposures
- lab exposures
Emerging infections
Increasing rapidly in incidence and geographic scope
Mechanisms:
1. Existing pathogen gains access to new host populations
2. New pathogen or subtypes
3. Environmental changes may contribute to emergence (ex: travel, climate change)
Incubation period
The time interval between exposure to an infectious agent and development of signs and symptoms
*Useful for determining the etiologic agent
Colonization
Agents multiply on the surface of the body without invoking tissue or immune response
Infestation
The presence of a living infectious agent on the bodies exterior surface on which a local reaction may occur
Infection
Agents have invaded host defenses invoking tissue and immune response
Stages of infection
Incubatory: (sub clinical) before signs and symptoms
Prodrome: later part of incubation period was symptoms appear but are nonspecific
Acute: signs and symptoms obvious
Resolution: symptoms improve
Convalescent: signs and symptoms disappear
Inapparent infection
No symptoms
Can still be transmitted to a susceptible host
Clinicians look for serologic evidence of infection
Types: Preclinical disease Subclinical disease Latent Persistent (chronic) disease
Iceberg concept of infection
Active clinical disease accounts for only a small proportion of hosts infections and exposures to disease agents
Herd immunity
Resistance of a group of people to the invasion and spread of a particular disease due to the immune status of a large portion of the population
Infection control in healthcare facilities
Immunization (staff) Sanitation (facility) Personal hygiene Hand washing PPE Food prep and storage
Hand hygiene
One of the most important ways to prevent the spread of infections
Standard precautions
Hand hygiene, PPE, safe injection practices
Transmission based precautions
Contact Droplet Airborne Syndromic Protective environment
Outbreak
A sudden start or increase of disease
Endemic
Usual prevalence of disease in a geographic area
Epidemic
Occurrence of disease in excess of normal expectancy
Pandemic
Worldwide epidemic
Reproductive number
The average number of new infections caused by one infected individual in a susceptible population
Nosocomial infection
Hospital acquired
Portals of Exit
Respiratory tract
GI tract
Genito-urinary tract
Percutaneous
HC management implications of emerging infections
Need to protect HCF patients/staff: -prompt identification/notification -PPE and other equipment needs -isolation/quarantine Need to manage influx of pts w/ novel infection: -surge capacity -staffing needs -diagnostic testing - available treatments/therapies
How to prevent disease
Destroy agent (pasteurization, chlorination etc.) Break cycle of transmission -eliminate means of transmission -reduce direct contact Increase immunization/resistance Reduce risk factors Isolate infectious cases
