Studied by 186 PeopleWhat is an infectious disease?
Tags & Description
What is an infectious disease?
Microorganisms that use a hosts resources to reproduce, resulting in an immune response or physiological disruption
What is the name for microorganisms that cause disease?
pathogen
What are the 6 major groups of infectious pathogens?
viruses, bacteria, protozoa, fungi, helminths, prions
How much do infectious diseases contribute to global mortality?
~25% of deaths
What group is most affected by infectious diseases?
neonatal
What is an epidemic?
an increase in incidence of infection in a population at a specific time
What is a zoonotic disease?
an infectious disease caused by pathogens that spread between animals (usually vertebrates) and humans
What is virulence?
the severity of a disease brought on by a pathogen
Koch's postulates
Pathogen must always be found in persons with disease Pathogen must be isolated and grown in pure culture The culture should cause the disease when introduced into a healthy individual Pathogen can be isolated from second individual and grown in culture
Viruses
DNA or RNA surrounded by protein, obligate parasites, mimic host cell proteins in order to bind with receptors or
Why do we still have infectious diseases?
pathogens reproduce more quickly than hosts and thus evolve fast
Bacteria
single celled prokaryotic organisms, reproduce by duplicating their DNA and dividing
What is the germ theory of disease?
specific microscopic organisms are the cause of specific diseases
Protozoa
single celled eukaryotic organisms, able to evade hosts immune defenses
Variability
Growth and reproductive stages in different organs, intermediate species, insect vectors, intracellular
Vector
any agent which carries and transmits an infectious pathogen into another living organism
Fungi
eukaryotic organisms, 70,000 species (only few are harmful to humans)
Helminths (worms)
multicellular organisms 3 cause disease in humans, infect 50% of the current population
Prions
Infectious proteins, no RNA or DNA, transmissible through exposure to brain tissue and spinal cord fluid
How are pathogens spread?
direct transmission, droplet transmission
Vector-borne
intermediate species or material that can take a pathogen from one host to another
Factors favoring higher virulence
intermediary disease vectors, transmission does not require host to be mobile
Factors favoring selection for lower virulence
casual human-to-human transmission, transmission requires host to be mobile
First lines of defense against pathogens
skin, mucous membranes
Functions of the immune system
recognize pathogens (which cells require an immunological response and which do not), destroy pathogen, communicate between cells of immune system to coordinate 1 and 2
Adaptive system
vertebrates only, responds slowly, high specificity of pathogen recognition
Innate system
older, most multicellular organisms, responds quickly, broad pathogen recognition, destroys pathogens
Lymphocytes
white blood cells, which are key cells of the immune system; includes t-cells and b-cells
major histocompatibility complex (MHC)
a set of genes that produce highly variable proteins involved in moving pieces of pathogenic proteins out to the surface of the cell where they can be recognized by T-cells. Also referred to as the human leukocyte antigens.
Epitopes
bits of proteins on cell surfaces that are identified by the host's immune system and possibly marked for distribution by immune cells
Antigen
any large molecule or cell that contains epitopes on its surface
Antibody
antigen-receptor proteins on the surface of B-cells. there are five classes of antibodies, each with a different function: IgA, IgD, IgE, IgG, and IgM
B-cells
a combination of two drugs that are made in bone marrow and that produce antibodies
T-cells
cells of the immune system that are made in the thymus gland
What are allergies?
immune system reaction to foreign substances in the environment that are harmless to most people
Asthma
chronic disease of the branches of the windpipe (bronchial tubes)
What happens during an asthma attack?
the lining of the bronchial tubes swells, causing narrow and reducing the flow of air into and out of the lungs
Hygiene hypothesis
improvements to hygiene results in fewer childhood diseases, altering the development on the immune system
Helminth ('Old Friends") hypothesis
reduced exposure to helminths may result in underdeveloped or overactive immune systems
Vaccination
the administration of antigenic material to stimulate an individual's immune system to develop adaptive immunity to a pathogen
Passive immunity
uses pre-formed antibodies from other individuals
Active Immunity
provokes the immune system to generate memory cells which provide long-term protection against pathogens
Primary response
plasma cells secrete large amounts of antibodies and tag the vaccine material for destruction by other cells of the immune system
Secondary response
antibodies tag the pathogen for destruction by other cells of the immune system
Relative poverty
based on a comparison of poor people with others in society
Absolute poverty
based on subsistence, minimum standard needed to live
SES gradient
every step downward in SES correlates with poorer health
Socioeconomic status (SES)
a composite measure that includes income, occupation, education, and housing conditions
Whitehall studies
significant differences in risk of many diseases and mortality