infectious disease Flashcards
two important characteristics used to classify infectious disease
reservoir
mode of transmission
reservoir
natural habitat of organism
mode of transmission
direct (human to human): sex, placenta, blood, skin, air(sneeze and coughs)
indirect (vector spread): water, food, animals, objects
incubation period
The time between exposure to an infectious agent and the onset of symptoms or signs of infection it is dependent on: Dose -Route -Rate of replication -Host
latent period
Time period from successful
infection until the development
of infectiousness
infectious period
Period following infection when
infection can be transmitted to
another susceptible host
serial interval
For diseases that are spread from person to person the time period between
successive generations
secondary attack rate
The proportion of susceptibles who develop infection within the
incubation period after exposure to a primary case
secondary infections/ people exposed(in contact with primary case)
pathogenicity
the ability of microbial agent to induce disease
illness rate= number with disease/ number with infection
virulence
severity of disease after infection occurs
immunogenicity
ability of organism to induce specific immunity
Basic reproductive number
expected number of secondary cases from a single case introduced into a susceptible population
-if less than 1- disease will disappear
-if =1 disease will be endemic
if greater than 1 disease will be epidemic
Net reproductive number
reproductive number at specified time
reproductive number is a function of
infectiousness
contact pattern
duration of infectiousness
proportion immune in the population
reproductive number (Ro) formula
probability of transmission in a contact between infected and susceptible individuals B
number of exposures of susceptible persons to infectious person per unit time-C
how long an infected person ins infectious -D