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Graph of herd immunity threshold vs basic reproduction number with selected diseases. S will be (1 − q), since q is the proportion of the population that is immune and q + S must equal one (since in this simplified model, everyone is either susceptible or immune). Then:
More specifically, infectivity is the extent to which the pathogen can enter, survive, and multiply in a host. It is measured by the ratio of the number of people who become infected to the total number exposed to the pathogen. [1] Infectivity has been shown to positively correlate with virulence, in plants. This means that as a pathogen's ...
Virus quantification is counting or calculating the number of virus particles (virions) in a sample to determine the virus concentration. It is used in both research and development (R&D) in academic and commercial laboratories as well as in production situations where the quantity of virus at various steps is an important variable that must be monitored.
The relationship between the latent period, the infectious period (the period of communicability) and the incubation period.In some diseases, as depicted in this diagram, the latent period is shorter than the incubation period.
Process Decision Program Chart (PDPC) is a technique designed to help prepare contingency plans.The emphasis of the PDPC is to identify the consequential impact of failure on activity plans, and create appropriate contingency plans to limit risks.
Epidemiological (and other observational) studies typically highlight associations between exposures and outcomes, rather than causation. While some consider this a limitation of observational research, epidemiological models of causation (e.g. Bradford Hill criteria) [7] contend that an entire body of evidence is needed before determining if an association is truly causal. [8]
A process flow diagram (PFD) is a diagram commonly used in chemical and process engineering to indicate the general flow of plant processes and equipment. The PFD displays the relationship between major equipment of a plant facility and does not show minor details such as piping details and designations.
The specific incubation period for a disease process is the result of multiple factors, including: [citation needed] Dose or inoculum of an infectious agent; Route of inoculation; Rate of replication of infectious agent; Host susceptibility; Immune response