17. infectious diseases

infectious agents

virus, bacteria, fungi, and parasites

outbreak

pathogen infects many people in one area over a short window of time

endemic

outbreak remains constant and predictable within specific population or environment

epidemic

a pathogen unexpectedly begins to infect large number of people in a community or region

pandemic

a pathogen spread over multiple countries or affects a large region of the world

transmission

transfer of the infectious agent to a new host

infectious disease

occurs when infection causes symptoms in the host

can be short and mild or long term and life threating

transmission of respiratory infections

aerosolization, larger droplets, fomites

vectors

organism that carry infectious pathogens from host to host

susceptibility to infection

involves host health status, host genetics, and host immune systems

host tropism

only species host can be infectious

tissue tropism

only specific cells or tissues can be infectious

reproductive rate

represent how efficiently and infectious agent can spread, defines the averge number of people one individual will infect

herd immunity

occurs when enough individuals are immune and act as a buffer against transmission

innate immunity

contacts firsts when breach in barrier

activate adaptive immunity

type 1

defense against intracellular bacteria, Protozoa, viruses

Innate: NK and ILC 1

adapt: Th1 and CTL

type 2

defense against helminths and venoms (allergy/asthma)

innate: ILC2

adapt: Th2, b cell

type 3

defense against extracellular bacteria and fungi

innate: iLC3

adapt: th17 and b cells

viruses

obligates, intracellular pathogen

enter host cell via cell surface receptors

antiviral activity innate response

nonspecific defense

AMP, type 1 INF, inflammasomes, NK cells

viral neutralizing antibodies

bind to virus, and block from binding to receptors or enteric cells

can prevent productive infection

can protect adjacent cells, when virus leaves host cell

viral control and cleanse

cell mediated immunity of viruses

CD4 and CD8

viral immune evasion

virus overcome IFN

TAP activity

immunosupression

changes surface antigen

extracellular bacterial infectious

AB provide serval strong amature of eliminaiton

intracellular bacteria infections

not as strongly affected by AB

active NK cells and macrophages

th1 type DTH response

bacteria immune evasion

attach to host cell

proliferation of bacterium

invasion of host tissue

toxin, damaging host cell

parasites

vary in sixe, bumber of cells, and intracellular ot extracellular

parasitic worms (helminths)

do not replicate in host — limiting immune engaments

type 2 response

IgE production

fungal disease

occurs via penetrating injury, inhalation or during immune disruption

primary or opportunistic pathogen

innate immunity primary control for infection 

primary pathogen

highly virulent and establish infection in healthy hose

opportunistic pathogen

weakly virulent and primarily infects infants with compromised immunity

C type lectin receptors

PRR, keep fungal cells in check

fungal immune evasion

capsules that prevent PRR binding

fungi-induced expulsion from macrophages