unit 3: infectious disease and stds Flashcards
chain of infection
-pathogen
-reservoir
-portal of exit
-means of transmission
-portal of entry
-new host
pathogen
-microorganism that causes disease bc produces toxins that harm human tissue; or directly invading body cells
-HIV, SARS, tuberculosis
reservoir
-pathogen’s natural environment
-can be a person, animal, environmental component (soil, water) that spreads infection
-can be ill or asymptomatic carrier
portal of exit
-where the pathogen leaves the reservoir (saliva, mucous membranes, blood, feces, nose and throat discharges)
-mumps, sti’s, hiv/hepatitis, colds, influenza
means of transmission
directly or indirectly
-direct: passed from one to another w/o an intermediary –> close association that isnt always physical contact (sneezing, coughing particles in air and smo inhales)
-sexual contact or contact w/ blood
-indirect: vectors
-insects, animals, organisms that carry pathogen from one host to another
-contaminated soil, food, water or inanimate objects
-in air for long periods of time
portal of entry
-enter in 3 ways:
-direct contact w/ or penetration of the skin
-inhalation thru mouth or nose
-ingestion of contaminated food or water
systemic infection
An invasion by a microorganism that spreads though the blood or lymphatic system to large portions of the body.
the new host
-factors determine if a pathogen can establish itself and cause infection
–> how resistant a person is/immunity, # of pathogens that enter the new host and how able the body’s defenses are
if conditions are right, a new chain of infection starts in the new host.
how to break the chain
-quarantine, killing insects or animals that carry pathogens , public sanitation practices, handwashing, use of face masks, immunization
physical and chemical barriers
body’s first line of defense
- skin prevents many microorganisms from entering the body
-mouth lined w/ mucous membranes which has cells that prevent passage of unwanted organisms + particles
-tears, saliva, vaginal secretions
-enzymes
-cilia–> if cells dmged, coughing is the only way of ridding airways of foreign particles
white blood cells
neutrophils, macrophages, natural killer cells, dendritic cells, lymphocytes
neutrophils
-travel in bloodstream to areas of invasion, attacking and ingesting pathogens
macrophages
- take up stations in tissues and act as scavengers (big eaters)
-devouring pathogens and worn-out cells
natural killer cells
-directly destroy virus-infected cells and calls that have turned cancerous
dendritic cells
-reside in tissues, eat pathogens and activate lymphocytes
lymphocytes
-travel in both bloodstream + lymphatic system
lymph nodes
-lymphatic system
-where macrophages and dendritic and filter bacteria
lymphatic system
-a network of vessels and organs, that pick up excess fluid and proteins, lipids + other particles from body tissues
-pass through lymph nodes to be cleansed and then returned to the bloodstream
lymphocytes
T cells, b cells
T cells: helper t cells, killer t cells, suppressor t cells
b cells
lymphocytes that produce antibodies
memory t + b cells
Lymphocytes generated during an initial infection that circulate in the body for years, remembering the specific antigens that caused the infection and quickly destroying them if they appear again.
antigens
Markers on the surface of a foreign substance that immune system cells recognize as non-self and that trigger the immune response.
the inflammatory response
-special cells release histamine, causing blood vessels to dilate and fluid to flow out of capillaries into injured tissue. Produces increased heat, swelling, and redness in the affected area. WBC attack invaders. site of infection may be pus (collection of dead white blood cells + debris)
the immune response (response and phases)
- natural (innate) + acquired (adaptive) response
-phase 1: viruses invade the body through a break in skin or other portal of entry + take over body cells in order to replicate
-phase 2: helper t cells trigger the production of killer T cells and B cells
-phase 3: killer t cells and natural killer cells destroy infected body cells. b cells produce antibodies that bind to viruses + mark for destruction by macrophages
-phase 4: when danger ends, suppressor t cells halt immune response. memory t and b cells reserved to make a quick response in case of future invasions
natural response
neutrophils, macrophages, dendritic cells, and natural killer cells
-recognize pathogens as “foreign” + have no memory of past infections: they respond the same way no matter how many times a pathogens
-eat invaders (destroying them internally)
acquired response
T and B cells
-change after one contact w/ pathogen and develop memory
immunity
Mechanisms that defend the body against infection; specific defences against specific pathogens.
acquired immunity
the ability of memory lymphocytes to remember previous infections
incubation
The period when bacteria or viruses are actively multiplying inside the body’s cells; usually a period without symptoms of illness.
prodromal period
-where symptoms first appear following incubation
how is fever caused
release and activation of certain cytokines in macrophages + other cells during the immune response
-cytokines travel in bloodstream to brain and cause body’s temp to reset to higher level
-elevated temp helps body fight against pathogens by enhancing immune responses
how does runny nose work
when your lymphocytes destroy infected mucosal cells –> inctreased mucus production
fatigue of flu?
caused by pro-inflammatory cytokines
how does contagion work
infectious microbes in body has access to another person + may be before vigorous immune response occurs and so you may be contagious before experiencing symptoms + knowing that youre infected
immunization
The process of conferring immunity to a pathogen by administering a vaccine.
types of vaccines
weakened virus: measles, mumps, rubella
killed virus (still produces antibodies): influenza
-portion of killed virus but enough for body to recognize and make antibodies against it (viral-vector vaccines) covid vacc by astrazeneca + johnson&johnson
mrna vaccines: deliver strand of messenger rna to patient, used to produce tiny portion of virus for immune system to recognize and make antibodies. covid vacc by moderna and pfizer
active imunnity
vaccinated person produces their own antibodies to the microorganism
passive immunity
a person exposed to disease is injected w/ antibodies produced by humans or animals who recovered from the disease
gamma globulin
-product made from blood plasma containing all antibodies ever made
-creates rapid but temporary immunity to a particular disease
-sometimes used to treat antibody deficiency syndromes
cause of allergies
hypersensitive and overactive immune systems to harmless substances
allergens
substances that provoke allergies
-may cause a response of they’re inhaled or swallowed or in contact w/ skin
where do allergic responses come from
production of antibody IgE (immunoglobulin E)
-initial exposure to a particular allergen may cause little response but sensitizes immune system by producing IgE and binds to mast cells which release histamine into surrounding tissues
histamine effects
-increasing inflammatory response + stimulating mucus production
but depends on what part of the body is affected
nose:
-congestion and sneezing
eyes:
-itchiness and tearing
skin:
-redness, swelling and itching
intestines:
-bloating and cramping
lungs
-coughing, wheezing, shortness of breath, some ppl an asthma attack
dealing w/ allergies
-avoidance: making changes in environment/behav
-medication: OTC antihistamines for blocked nasal, sinus, or middle ear passages, prescription corticosteroids
-immunotherapy: allergy shots
bacteria
microscopic single-celled organisms
-most feed on dead matter and play an important role in recycling of nutrients for other organisms
-others feed on living things and cause disease
-may be bacili (rod shaped)
-cocci (spherical)
-spirochete (viral)
-vibrios (comma shaped)
-pneumonia, meningitis, strep throat, toxic shock, mrsa, tuberculosis, tick-borne infections, ulcers, chlamydia
viruses
infectious agents consisting of a protein shell enclosing dna or rna
-reproduce only within a host cell
-lack independent metabolism
-PARASITE: take what they need for growth and reproduction from the cells they invade
-when in host cell, sheds protein covering and genetic material takes over to reproduce
-cause of most contagious diseases
-common cold, influenza, measles, mumps, rubella, chicken pox, cold sores, herpesvirus, hepatitis, hsv, polio, rabies, hpv
fungi
single or multi-celled organisms
-absorbs food from organic matter
-yeast infection, athletes foot, ringworm, jock itch, valley fever
protozoa
single celled organisms
-diseased in mostly developing countries
-malaria, giardiasis
parasitic worms
worms that feed and live on or in a host
-tapeworm, pinworm, hookworm
-originate from contaminated food/drink
prlons
proteinaceous infectious particles
-lack dna/rna and consist only of protein
-presence does not trigger an autoimmune response
-degenerate cns and forms deposits in the brain
-spreads by triggering normal proteins to change structure to their abnormal and dmging form
-class of disease: TSE
-CJD, BSE (mad cow disease), vcjd (from cows w/ bse)
-resistant to heat, radiation and chemicals that kill other pathogens bc of long incubation period (50 yrs)
antibiotics
naturally occurring or synthetic substances that can kill bacteria
-interrupt production of new bacteria by dmging their reproductive cycle or cause faulty parts to be made or inhibiting production of certain proteins
antibiotic resistance
pathogens may be resistant to antibiotic effects thru mutation or transfer of genetic material from one to another
-gonorrhea, salmonellosis, a strain of tuberculosis,
INEFFECTIVE AGAINST VIRUSES
cause of resistance
-when ppl fail to take full course of antibiotic
-misuse for viral infections
-use of anti in agriculture
how viruses are fought off
interferon is produced by immune system
how to treat viruses
-antiviral drugs
-interferes by preventing a virus from entering body cells to reproduce
emerging infectious diseases
-diseases w increased/threatens infection in near future
-tuberculosis, cholera, ebola, west nile virus, zika virus, monkeypox, SARS, COVID, ecoli, rotavirus, hantavirus
what factors contribute to emerging infections
-drug resistance
poverty
poor public health measures
travelling
mass food production/distribution
human behav
-bioterrorism
climate change
autoimmune diseases
body comes under attack by its own cells or when body confuses its own cells w/ foreign organisms
-immune system is too sensitive and misapprehends itself as nonself
-cancer, lupus, arthritis,
epidemiology
The study of the determinants of health; deals with the incidence, distribution, and control of factors relating to health + disease
methods of covid transmission
-aerosol: exhaled units of less than or equal to 5 micrometers lingering in air for hours
-droplet: exhaled units of more than 5 micrometers fall to ground within 1-2 metres
fomite: units on inert surface, touched by a potential host who transfers it to their own mucous membrane
cfr + ifr
case fatality ratio
-fraction of cases that die (known)
infection fatality ratio
-fraction of ALL cases that die including cases not known
-incorporates all infections and deaths never measured (estimate)
TPR
test positivity rate
-fraction of cases conducted that came back positive –> tells how hard to look to find an infected person
-rough estimate of how deeply the disease is penetrating in a pop
- higher = easier it is to come across an infection
r
reproduction #
-avr number of new cases that a current case will infect before smos current infection resolves
-if greater than 1, epidemic is experiencing exponential growth
- if r = 1, disease is in a steady state
-if r is less than 1 then epidemic is on its way to dying
- if r = 2, each infected person infects 2 additional ppl before case is resolved
