When a parasite or pathogen is multiplying in or on a host
Infection
Host cannot function ormally due to the presence of parasites or its products
Infectious Disease
Cause Disease
Pathogens
An organisms abilty to cause disease
Pathogenicity
Degree or intensity of pathogenicity, as indicated by mobidity and mortality rates
Virulence
What affects host and parasite relationship
Amount of organisms
Virulence ability
Hosts degree of resistance (lifestyle, immunocompromised, living condtns)
Symptoms
Very subjective, determined by patient. Cannot be measured (pain, feelings)
Sign
Objective. Measured or seen. (fever, rash, cough)
Disease Syndrome
Combination of symptoms and signs
Incubation period
No symptoms or signs yet
Prodromal Stage
Early Signs and Symptoms (usally felt the day before when youll feel the signs and symptoms)
Illness period
Majority of signs and symptoms
Convalescence
Recovery from disease
What is the earliest stage a disease cna be considered infectious
Incubation period at earliest. dont even have signs or symptoms yet
What is the latests stage a disease can be considered infctious
Convalescence period. weeks to months even after youre feeling better
What does it mean when we way that most infections are sublcinical
No signs or symptoms, and can only be deteced by tests
Factors that affect virulence
Infectivity: ability to start an infection
- ability to transmit to new host
- ability to adhere to host
- ability to replicate
- ability to evade immune system
Invasiveness: ability to spread within host
Pathogenic Potential: ability to cause signs and symptoms
Transmission Methods
Direct: Close contact with infected person
Indirect: Mother to fetus
Vector: vector transmission
Airborne: particles maintained in the air
Fomites: contaminated objects
Adhering Methods
Fimbriae
Pili
Capsule
S Layer (proteins)
Teichoic acid (G+)
Vrial capsid and envelopes
Correct environment to replicate in a host
- Proper pH, O2 Content, and Temperature
How do pathogens evade host immune system
- Cleaves antibodies
- Lyses WBC
- Inhibit phagocytosis (capsule)
- Hide within host cells
Things thatt privide an organism’s ability to spread within a host
Enzymes that damage host tissues
Neurotoxin
Affect neurvous system
ex: botulism and tetanus
Enterotoxin
Affect the GI tract
ex: cholera, and ecoli stop water uptake lads to diarrhea
