A2.3

wścieklizna

rabies

outbreak

unexpected increase in number of people with a specific condition

epidemic

when an outbreak has spread over a large geographical area

pandemic

an rpidemic that has gone global over a large exponential growth

epidemiology

study of the occurrence, distribution and control of a disease in a population

viruses features

most abundant biological entity, small fixed size, contail nucleic acid, enclosed by a capsid, no cytoplasm, could have envelope, obligatory intracelluar parasites (organism that benefits from another one - one way)

host cell

the cell uses to carry out its metovbolic and reproductive process

the lytic cycle

attachment, dna entry, dna replication, dna transtription, protein synthesis, lysis, spread

lysogenic cycle

attachment, dna entry, integration, cell division

when the dna of virus and cell integrate

prophage

too virulent

run out of hosts

not virulent enough

immune system will kill them

progressive hypothesis

viruses evolved from modified cell components

regressive

viruses evolved from the loss of cell components

reason why viruses evolve rapidly

short generation time, lots of mutation, natural selection favours viruses with genetic traits that help it evade detection

antigens

proteins on the virus surface used for attaching to host cells

reverse transcriptase

rna reverse transtripted into dna without proofreading (stays forever)

hiv

human immunodeficiency virus

capsid

protects dna

tail sheat

contract - become shorter and longer

tail fibre

attach host cell

pins

puts dna into cell, cooperate with tail sheath which shots the pin into the bacteria