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HLW
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What host cannot spread the infection to other susceptible hosts under natural conditions?
dead end host
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What is defined as encounter of a potentially pathogenic agent with susceptible animal host and host shows IMMUNE RESPONSE to infection?
infection
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What is time period between exposure to agent (infection) and onset of clinical signs?
incubation period
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What is time between initiation of infection in host and when host becomes infectious to others (sheds agent)?
latent period
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What is time during which host is infectious to others; from 1st shed to end of disease?
period of transmission/communicability
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What is clinically apparent infection/overt illness?
disease (one possible outcome of infection)
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What are 4 possible outcomes to exposure to infectious agent?
- immune
- clinical
- subclinical
- carrier
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What are 3 criteria for defining a case?
- clinical syndrome (symptoms)
- immune response (info on time of exposure)
- agent detection (by lab confirmation)
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What is an infection in susceptible host without clinical signs? What would be required to show presence of infection?
- subclinical infection
- antibody response
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Does a carrier have clinical signs? Can they shed to others?
- no symptoms
- yes, shed to others
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What refers to small gradual changes that occur through point mutations? These minor changes account for annual epidemics.
antigenic drift
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What is an abrupt, major change to produce novel subtypes via genetic reassortment?
antigenic shift
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What is the ability of an organism to cause infection in susceptible host? How would you calculate this?
infectivity = infected people / exposed people
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What is the infectivity during an outbreak called? how do you calculate? Is this typically for acute or chronic disease?
- attack rate = # new cases for epidemic period/ entire pop at risk
- acute disease
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What provides a measure of a disease's ability to spread?
secondary attack rate (primary cases spread to cause secondary ones)
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What is proportion of infected people that develop clinical signs? How to calculate?
pathogenicity = # infected and exhibiting signs / total number infected
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What is number of persons that develop severe disease?
virulence
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What is the proportion of cases that eventually die from disease? How to calculate?
case fatality ratio = # fatal cases/ # of cases with disease
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What is incidence of death among all individuals in population? Calculate?
mortality rate = # fatal cases / total population
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What is the ability of agent to induce immune response, and how do you measure if there is a response?
- immunogenicity
- evaluate antibody production
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