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In epidemiology, a rate ratio, sometimes called an incidence density ratio or incidence rate ratio, is a relative difference measure used to compare the incidence rates of events occurring at any given point in time. It is defined as:
Calculating the infection rate is used to analyze trends for the purpose of infection and disease control. [1] An online infection rate calculator has been developed by the Centers for Disease Control and Prevention that allows the determination of the streptococcal A infection rate in a population.
In epidemiology, force of infection (denoted ) is the rate at which susceptible individuals acquire an infectious disease. [1] Because it takes account of susceptibility it can be used to compare the rate of transmission between different groups of the population for the same infectious disease, or even between different infectious diseases.
Incidence should not be confused with prevalence, which is the proportion of cases in the population at a given time rather than rate of occurrence of new cases. Thus, incidence conveys information about the risk of contracting the disease, whereas prevalence indicates how widespread the disease is.
Human infectious diseases may be characterized by their case fatality rate (CFR), the proportion of people diagnosed with a disease who die from it (cf. mortality rate).It should not be confused with the infection fatality rate (IFR), the estimated proportion of people infected by a disease-causing agent, including asymptomatic and undiagnosed infections, who die from the disease.
A case fatality ratio is a comparison between two different case fatality rates, expressed as a ratio. It is used to compare the severity of different diseases or to assess the impact of interventions. [6] Because the CFR is not an incidence rate by not measuring frequency, some authors note that a more appropriate term is case fatality ...
It is defined as the inverse of the absolute risk increase, and computed as / (), where is the incidence in the treated (exposed) group, and is the incidence in the control (unexposed) group. [1] Intuitively, the lower the number needed to harm, the worse the risk factor, with 1 meaning that every exposed person is harmed.
In epidemiology, the attack rate is the proportion of an at-risk population that contracts the disease during a specified time interval. [1]