13. epidemiology

Question 1

endemic disease

Answer 1

constanly present at low levels eg colds

Question 2

epidemic disease

Answer 2

sudden increase above expected eg chickenpox

defined as more than 400 cases per 100000 of population per week

Question 3

pandemic

Answer 3

increase simultaneously globally

Question 4

morbidity rate

Answer 4

number of individuals becoming ill

Question 5

mortality rate

Answer 5

relationship between deaths and cases

Question 6

two types of epidemic

Answer 6

common source epidemic- sharp rise to peak and rapid decline eg food poisoning
propagated epidemic - slow rise and gradual decline eg chickenpox in winter/spring

Question 7

herd immunity

Answer 7

resistance of a population to infection Is due to immunity of the majority

Question 8

influences on herd immunity

Answer 8

organism and environment can all change over time
change in the organism
antigenic drift ]
antigenic shift

Question 9

antigenic drift

Answer 9

influences herd immunity
minor antigenic variation due to mutations alters amino acid sequences
eg in flu if haemagluttinin and neuraminidase spikes change could alter ability to attach to pre-existing antibodies to these proteins

Question 10

antigenic shift in flu virus

Answer 10

Flu virus genome is 8 segments of RNA

undergoes frequent reassortment, gene exchange between different strains and causes major changes in virus coat proteins

Question 11

how could the next flu pandemic begin

Answer 11

antigenic shift will occur again
in 2009 mexico between human pig and bird flu
a reassortment (mixing of RNA) lead to a new strain infecting humans H1N1

Question 12

control of epidemics

Answer 12

eliminate source
break connection between source and host
vaccinate to raise level of herd immunity

Question 13

emergence of new diseases

Answer 13

HIV AIDs
ebola
legionnaires (common source outbreaks)
ecoli O157

Question 14

re-emergence of old diseases

Answer 14

old diseases which we have known about for a long time
tuberculosis and diptheria
hospital acquired infections (nosocomial) eg rise in antibiotic resistance MRSC methicillin resistant staphylococcus aureus and re emerging infection

Question 15

factors responsible dor emergence of new pathogens and re emergence of old known pathogens

Answer 15

demographics (move to crowded cities)
transportation (bulk processing and speed of spread)
economic development and changes in land use (eg building a dam to mosquitoes to disease)
international travel
biological warfare
breakdown of public health services
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