Summary​ ​of​ ​Infectious​ ​Diseases
Viruses
● Describe​ ​how​ ​a​ ​virus​ ​reproduces​ ​inside​ ​a​ ​cell.
Viruses​ ​can​ ​only​ ​reproduce​ ​in​ ​living​ ​cells.​ ​A​ ​particular​ ​strain​ ​of​ ​virus​ ​may​ ​only​ ​attack​ ​specific
cells​ ​-​ ​but​ ​these​ ​may​ ​be​ ​plant​ ​cells,​ ​animal​ ​cells​ ​or​ ​bacterial​ ​cells.​ ​For​ ​example,​ ​common
colds​ ​are​ ​caused​ ​by​ ​viruses​ ​which​ ​attack​ ​cells​ ​in​ ​the​ ​respiratory​ ​s​ystem​.
These​ ​are​ ​the​ ​main​ ​stages:
1.
2.
3.
4.
the​ ​virus​ ​attaches​ ​itself​ ​to​ ​a​ ​specific​ ​host​ ​cell​ ​(the​ ​cell​ ​in​ ​which​ ​it​ ​will​ ​reproduce)
the​ ​virus​ ​injects​ ​its​ ​genetic​ ​material​ ​into​ ​the​ ​host​ ​cell
the​ ​host​ ​cell​ ​uses​ ​the​ ​genetic​ ​material​ ​to​ ​make​ ​new​ ​viruses
the​ ​host​ ​cell​ ​splits​ ​open,​ ​releasing​ ​the​ ​viruses
● Explain​ ​the​ ​two​ ​ways​ ​white​ ​blood​ ​cells​ ​can​ ​kill​ ​pathogens.
ingest​ ​pathogens​ ​and​ ​destroy​ ​them
produce​ ​antibodies​ ​to​ ​destroy​ ​pathogens
produce​ ​antitoxins​ ​that​ ​neutralise​ ​the​ ​toxins​ ​released​ ​by​ ​pathogens
Note​ ​that:
the​ ​pathogens​ ​are​ ​not​ ​the​ ​disease​ ​-​ ​they​ ​cause​ ​the​ ​disease
white​ ​blood​ ​cells​ ​do​ ​not​ ​eat​ ​the​ ​pathogens​ ​-​ ​they​ ​ingest​ ​them
antibodies​ ​and​ ​antitoxins​ ​are​ ​not​ ​living​ ​things​ ​-​ ​they​ ​are​ ​specialised​ ​proteins
● Explain​ ​how​ ​we​ ​become​ ​immune​ ​to​ ​a​ ​disease​ ​and​ ​how​ ​a​ ​vaccine​ ​works.
Vaccines​​ ​greatly​ ​reduce​ ​the​ ​risk​ ​of​ ​infection​ ​by​ ​working​ ​with​ ​the​ ​body's​ ​natural​ ​defenses​ ​to
safely​ ​develop​ ​immunity​​ ​to​ ​disease​.​ ​To​ ​understand​ ​how​ ​vaccines​ ​work​,​ ​it​ ​is​ ​helpful​ ​to​ ​first
look​ ​at​ ​how​ ​the​ ​body​ ​fights​ ​illness​.​ ​When​ ​germs,​ ​such​ ​as​ ​bacteria​ ​or​ ​viruses,​ ​invade​ ​the​ ​body,
they​ ​attack​ ​and​ ​multiply.
● Describe​ ​how​ ​Edward​ ​Jenner​ ​discovered​ ​the​ ​vaccine​.
​ ​ ​This​ ​paper​ ​explores​ ​the​ ​history​ ​of​ ​vaccines​ ​and​ ​immunization,​ ​beginning​ ​with​ ​Edward
Jenner’s​ ​creation​ ​of​ ​the​ ​world’s​ ​first​ ​vaccine​ ​for​ ​smallpox​ ​in​ ​the​ ​1790s.​ ​We​ ​then​ ​demonstrate
that​ ​many​ ​of​ ​the​ ​issues​ ​salient​ ​in​ ​Jenner’s​ ​era—such​ ​as​ ​the​ ​need​ ​for​ ​secure​ ​funding
mechanisms,​ ​streamlined​ ​manufacturing​ ​and​ ​safety​ ​concerns,​ ​and​ ​deep-seated​ ​public​ ​fears​ ​of
inoculating​ ​agents—have​ ​frequently​ ​reappeared​ ​and​ ​have​ ​often​ ​dominated​ ​vaccine​ ​policies.
We​ ​suggest​ ​that​ ​historical​ ​awareness​ ​can​ ​help​ ​inform​ ​viable​ ​long-term​ ​solutions​ ​to
contemporary​ ​problems​ ​with​ ​vaccine​ ​research,​ ​production,​ ​and​ ​supply.
Bacteria
Describe​ ​how​ ​bacteria​ ​reproduce
● Bacteria​ ​can​ ​reproduce​ ​very​ ​quickly​ ​given​ ​the​ ​right​ ​conditions,​ ​such​ ​as​ ​warmth,
moisture​ ​and​ ​suitable​ ​nutrients.​ ​Huge​ ​numbers​ ​of​ ​bacteria​ ​can​ ​be​ ​grown
commercially​ ​in​ ​large​ ​containers​ ​called​ ​fermenters​.​ ​Smaller​ ​numbers​ ​can​ ​be​ ​cultured
in​ ​the​ ​lab​ ​by​ ​growing​ ​them​ ​on​ ​agar​ ​plates
Describe​ ​how​ ​bacteria​ ​can​ ​become​ ​resistant​ ​to​ ​antibiotics.
● Bacterial​ ​strains​ ​can​ ​develop​ ​resistance​ ​to​ ​antibiotics.​ ​This​ ​happens​ ​because​ ​of​ ​natural
selection.​ ​In​ ​a​ ​large​ ​population​ ​of​ ​bacteria,​ ​there​ ​may​ ​be​ ​some​ ​cells​ ​that​ ​are​ ​not
affected​ ​by​ ​the​ ​antibiotic.​ ​These​ ​cells​ ​survive​ ​and​ ​reproduce,​ ​producing​ ​even​ ​more
bacteria​ ​that​ ​are​ ​not​ ​affected​ ​by​ ​the​ ​antibiotic.
Comment​ ​on​ ​the​ ​benefits​ ​and​ ​limitations​ ​of​ ​antibiotic​ ​use.
● Antibiotics​ ​are​ ​substances​ ​that​ ​kill​ ​bacteria​​ ​or​ ​prevent​ ​their​ ​growth.​ ​They​ ​do​ ​not
work​ ​against​ ​viruses​.​ ​It​ ​is​ ​difficult​ ​to​ ​develop​ ​drugs​ ​that​ ​kill​ ​viruses​ ​without​ ​damaging
the​ ​body’s​ ​tissues​.
● Outline​ ​Fleming's​ ​role​ ​in​ ​the​ ​discovery​ ​of​ ​antibiotics​ ​(Penicillin).
● The​ ​first​ a​ ntibiotic,​ ​penicillin,​ ​was​ ​discovered​ ​by​ ​Alexander​ ​Fleming​ ​in​ ​1928.​ ​He
noticed​ ​that​ ​some​ ​bacteria​ ​he​ ​had​ ​left​ ​in​ ​a​ ​petri​ ​dish​ ​had​ ​been​ ​killed​ ​by​ ​naturally
occurring​ ​penicillium​ ​mould.
● Since​ ​the​ ​discovery​ ​of​ ​penicillin,​ ​many​ ​other​ ​antibiotics​ ​have​ ​been​ ​discovered​ ​or
developed.​ ​Most​ ​of​ ​those​ ​used​ ​in​ ​medicine​ ​have​ ​been​ ​altered​ ​chemically​ ​to​ ​make
them​ ​more​ ​effective​ ​and​ ​more​ ​safe​ ​for​ ​humans.
Microbes​ ​and​ ​Pathogens
Define​ ​they​ ​terms​ ​microorganisms,​ ​microbes​ ​and​ ​pathogens.
Pathogens:​ ​Pathogens​ ​are​ ​microorganisms​​ ​that​ ​cause​ ​infectious​ ​disease.​ ​Bacteria​ ​and​ ​viruses
are​ ​the​ ​main​ ​pathogens.
Microbes:​ ​a​ ​microorganism,​ ​especially​ ​a​ ​bacterium​ ​causing​ ​disease​ ​or​ ​fermentation.
Microorganism-​ ​a​ ​microscopic​ ​organism,​ ​especially​ ​a​ ​bacterium,​ ​virus,​ ​or​ ​fungus.
Outline​ ​the​ ​4​ ​main​ ​types​ ​of​ ​pathogens​ ​(bacteria,​ ​viruses,​ ​fungi​ ​and​ ​protozoa)​ ​and​ ​give
examples​ ​of​ ​diseases​ ​caused​ ​by​ ​them.
Fungi​ ​Bacteria​ ​–
Virus​ ​–
Protozoa​ ​-
Our​ ​Body's​ ​Defences
● Outline​ ​the​ ​barriers​ ​to​ ​the​ ​entry​ ​of​ ​microbes​ ​into​ ​our​ ​body​ ​(skin,​ ​mucus,​ ​tears,
stomach​ ​acid)
● Outline​ ​the​ ​necessity​ ​of​ ​personal​ ​hygiene.
Defenses​​ ​Against​ ​Infection.​ ​Natural​ ​barriers​ ​and​ ​the​ ​immune​ ​system​ ​defend​ ​the​ ​body​​ ​against
organisms​ ​that​ ​can​ ​cause​ ​infection.​ ​Natural​ ​barriers​ ​include​ ​the​ ​skin,​ ​mucous​ ​membranes,
tears,​ ​earwax,​ ​mucus,​ ​and​ ​stomach​ ​acid.​ ​Also,​ ​the​ ​normal​ ​flow​ ​of​ ​urine​ ​washes​ ​out
microorganisms​ ​that​ ​enter​ ​the​ ​urinary​ ​tract.
● Natural​ ​barriers​ ​and​ ​the​ ​immune​ ​system​ ​defend​ ​the​ ​body​ ​against​ ​organisms​ ​that​ ​can​ ​cause
infection.
● Natural​ ​barriers​ ​include​ ​the​ ​skin,​ ​mucous​ ​membranes,​ ​tears,​ ​earwax,​ ​mucus,​ ​and​ ​stomach
●
●
●
●
acid.​ ​Also,​ ​the​ ​normal​ ​flow​ ​of​ ​urine​ ​washes​ ​out​ ​microorganisms​ ​that​ ​enter​ ​the​ ​urinary​ ​tract.
Usually,​ ​the​ ​skin​​ ​prevents​ ​invasion​ ​by​ ​microorganisms​ ​unless​ ​it​ ​is​ ​damaged—for​ ​example,
by​ ​an​ ​injury,​ ​insect​ ​bite,​ ​or​ ​burn.
Mucous​ ​membranes,​​ ​such​ ​as​ ​the​ ​lining​ ​of​ ​the​ ​mouth,​ ​nose,​ ​and​ ​eyelids,​ ​are​ ​also​ ​effective
barriers.​ ​Typically,​ ​mucous​ ​membranes​ ​are​ ​coated​ ​with​ ​secretions​ ​that​ ​fight​ ​microorganisms.
For​ ​example,​ ​the​ ​mucous​ ​membranes​ ​of​ ​the​ ​eyes​ ​are​ ​bathed​ ​in​ ​tears,​ ​which​ ​contain​ ​an
enzyme​ ​called​ ​lysozyme​ ​that​ ​attacks​ ​bacteria​ ​and​ ​helps​ ​protect​ ​the​ ​eyes​ ​from​ ​infection.
The​ ​airways​​ ​filter​ ​out​ ​particles​ ​that​ ​are​ ​present​ ​in​ ​the​ ​air​ ​that​ ​is​ ​inhaled.​ ​The​ ​walls​ ​of​ ​the
passages​ ​in​ ​the​ ​nose​ ​and​ ​airways​ ​are​ ​coated​ ​with​ ​mucus.​ ​Microorganisms​ ​in​ ​the​ ​air​ ​become
stuck​ ​to​ ​the​ ​mucus,​ ​which​ ​is​ ​coughed​ ​up​ ​or​ ​blown​ ​out​ ​of​ ​the​ ​nose.​ ​Mucus​ ​removal​ ​is​ ​aided​ ​by
the​ ​coordinated​ ​beating​ ​of​ ​tiny​ ​hairlike​ ​projections​ ​(cilia)​ ​that​ ​line​ ​the​ ​airways.​ ​The​ ​cilia
sweep​ ​the​ ​mucus​ ​up​ ​the​ ​airways,​ ​away​ ​from​ ​the​ ​lungs.
The​ ​digestive​ ​tract​​ ​has​ ​a​ ​series​ ​of​ ​effective​ ​barriers,​ ​including​ ​stomach​ ​acid,​ ​pancreatic
enzymes,​ ​bile,​ ​and​ ​intestinal​ ​secretions.​ ​These​ ​substances​ ​can​ ​kill​ ​bacteria​ ​or​ ​prevent​ ​them
●
from​ ​multiplying.​ ​The​ ​contractions​ ​of​ ​the​ ​intestine​ ​(peristalsis)​ ​and​ ​the​ ​normal​ ​shedding​ ​of
cells​ ​lining​ ​the​ ​intestine​ ​help​ ​remove​ ​harmful​ ​microorganisms.
The​ ​urinary​ ​tract​​ ​also​ ​has​ ​several​ ​effective​ ​barriers.​ ​The​ ​bladder​ ​is​ ​protected​ ​by​ ​the
urethra,​ ​the​ ​tube​ ​that​ ​drains​ ​urine​ ​from​ ​the​ ​body.​ ​In​ ​males​ ​older​ ​than​ ​6​ ​months,​ ​the​ ​urethra
is​ ​long​ ​enough​ ​that​ ​bacteria​ ​are​ ​seldom​ ​able​ ​to​ ​pass​ ​through​ ​it​ ​to​ ​reach​ ​the​ ​bladder,​ ​unless
the​ ​bacteria​ ​are​ ​unintentionally​ ​placed​ ​there​ ​by​ ​catheters​ ​or​ ​surgical​ ​instruments.​ ​In​ ​females,
the​ ​urethra​ ​is​ ​shorter,​ ​occasionally​ ​allowing​ ​external​ ​bacteria​ ​to​ ​pass​ ​into​ ​the​ ​bladder.​ ​In
●
●
both​ ​sexes,​ ​when​ ​the​ ​bladder​ ​empties,​ ​it​ ​flushes​ ​out​ ​any​ ​bacteria​ ​that​ ​reach​ ​it.