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In epidemiology, the basic reproduction number, or basic reproductive number (sometimes called basic reproduction ratio or basic reproductive rate ), denoted (pronounced R nought or R zero ), [1] of an infection is the expected number of cases directly generated by one case in a population where all individuals are susceptible to infection. [2]
In mathematics, the Pythagorean theorem or Pythagoras' theorem is a fundamental relation in Euclidean geometry between the three sides of a right triangle. It states that the area of the square whose side is the hypotenuse (the side opposite the right angle) is equal to the sum of the areas of the squares on the other two sides.
Lethal dose. In toxicology, the lethal dose ( LD) is an indication of the lethal toxicity of a given substance or type of radiation. Because resistance varies from one individual to another, the "lethal dose" represents a dose (usually recorded as dose per kilogram of subject body weight) at which a given percentage of subjects will die.
In epidemiology, particularly in the discussion of infectious disease dynamics (modeling), the latent period (also known as the latency period or the pre-infectious period) is the time interval between when an individual or host is infected by a pathogen and when that individual becomes infectious, i.e. capable of transmitting pathogens to ...
Case fatality rate. In epidemiology, case fatality rate ( CFR) – or sometimes more accurately case-fatality risk – is the proportion of people who have been diagnosed with a certain disease and end up dying of it. Unlike a disease's mortality rate, the CFR does not take into account the time period between disease onset and death.
Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or radiation, and when symptoms and signs are first apparent. [1] In a typical infectious disease, the incubation period signifies the period taken by the multiplying organism to reach a threshold ...
Median lethal dose. In toxicology, the median lethal dose, LD50 (abbreviation for " lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. [1] The value of LD 50 for a substance is the dose required to kill half the members of a tested population after a specified test ...
Infectivity. In epidemiology, infectivity is the ability of a pathogen to establish an infection. 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.