Lecture 20 - epidimiology Flashcards
what is an endemic
constantly present
low level frq of disease at regular intervals
e.g. colds, human flu
what is an epidemic
sudden increase above expected rates of disease
pandemic
increase simultaneously over a wide area (global)
what were the 4 flu pandemics since 20th C
spanish flu
asian flu
hong kong flu
swine flu
what disease wiped out all the froggys
chytridiomycosis panzootic
a fungal disease
some examples of plant pandemics
- maize lethal necrosis
- rice tungro
- sweet potato virus
- banana bunchy top wtf
- plum pox
what are the 2 things that need to be measured to measure frq of infection
- morbitity rate = no. becoming ill
- mortality rate = % those ill dying
how many cases classes an epidemic
over 400cases per 100k population per week
what are the 2 types of epidemic
- common source epidemic = sharp rise, sharp decline
- propagated epidemic = slow rise and slow decline
an example of common source epidemic
legionnaires disease (collecting towers bact, infects people)
what is herd immunity
resistance of a population to infection due to immunity of the majority
how many % people need to be immunised for herd immunity to flu
90%
cuz highly contagious
why might even a 90-95% vaccinated pop (the required for herd immunity) still not be protected from measles
might not be an even distribution across the pop
how many people need to be susceptible (un vaccinated) for measles to be sustained in a community
250-300K
what is antigenic drift
minor antigenic variation sue to mutations
what are the 2 antigen types on flu virus
haemagglutinin and neuraminidase
actual name of influenza virus
orthomyxovirus
diff between antigenic shift and drift
drift is accumulation of minor mutatitions
shift is mixture of genes in influenza virus
how does antigenic shift occur in flu
2 strains infect same cell
in cel form diff H and N combo
ta da new strain
what strain resulted in Mexico 2009 after antigenic shift
H1N1
caused lots of deaths
mix between human pig and bird flu
3 types of control measures taken in epidemic
eliminate source
break connection between source and host
raise level of herd immunity
what are examples of emerging diseases
emerging is NEW
- HIV
- Ebola
- Legionnaires disease
- E.coli O157
- Zika
what ways can zika virus be transmitted
- mosquito vector
- sexual transmission
- blood transfusion
- vertical transmission (preg mum to baby
= birth defects
what type of virus are all emerging viruses
RNA viruses
becuase
easily mutate
what are 3 diseases that have shown reemergence
TB
Diptheria
hospital acquired infections - MRSA (due to rise in antibiotic resistance)
what are some reasons for emergence of new pathogens and remergence of old ones
- more city living = crowded
- bulk processing and transportation
- changes in land use e.g. dams = mosquitos
- international travel
- microbial mutations
- bad weather causing public health measure breakdown
- biological warfare
