| Analysis and approaches | Number of times required | Definition |
|---|---|---|
| (Incidence) rate | 1 |
Ratio in which the denominator is the number of animal‐time units at riska Also, a ratio in which the denominator is time. E.g. cases/day, cases/week, etc. |
| Attack rates | 2 | It is the risk of becoming infected (case) during a specific period of time, such as the duration of an outbreak. It is calculated by dividing the total number of new cases by the total number of individuals at risk (total population exposed) |
| Attributable fraction | 1 | Proportion of disease in exposed individuals that is due to the exposure OR proportion of disease in the exposed group that would be avoided if the exposure were removeda |
| Attributable risk | 1 | Risk of disease in the exposed group MINUS the risk of disease in the non‐exposed group (i.e. increased or decreased probability of disease in the exposed groupa |
| Case fatality rate | 1 |
Proportion of animals with a specific disease that die from it (within a specific time period) It's a risk measure. Used to describe the impact |
| Count | 1 | Simple enumeration of the number of cases of disease or number of animals affected with a condition in a given population. |
| Descriptive risk mapping | 1 | For aggregated data. Crude risk or risk ratios can be calculated and reported in maps. |
| Distribution maps | 1 | Simple geographical representation of a given parameter (e.g. prevalence) or event (e.g. disease notification)a |
| Freedom from disease | 2 | It is an approach based on the Binomial distribution, used in areas where the disease or a pathogen is not circulating, for different purposes, e.g. estimation of the confidence on the free status of a given disease, the calculation of the required sample size to demonstrate freedom, etc |
| Hazard ratio | 2 | In survival analysis, the hazard ratio is the ratio of the hazard rates corresponding to the conditions described by two levels of an explanatory variable. Hazard ratios have similar interpretations to odds ratios and risk ratiosa |
| Incidence count | 1 | Enumeration of new cases in a population during certain timea |
| Incidence rate | 2 | Number of new cases of disease in a population per unit of animal‐time during a given time period. Eg. No. cases/No. animal‐daysa |
| Incidence rate ratio/Incidence density | 1 | Ratio of the disease frequency (measured as incidence rate) in an exposed group to the Incidence Rate in a non‐expose groupa |
| Incidence risk/Cumulative incidence | 1 | Probability that an individual animal will contract or develop a disease in a defined time period. Also referred to as ‘cumulative incidence’a |
| Incidence times | 1 | Times at which incident cases occur. Usually measured as the elapsed time since a reference event (e.g. calving)a |
| Modelling techniques | 8 | The adaptation of a parametric model to empirical distributions in order to estimate the parameters and operate probabilistic calculations |
| Odds | 1 | Ratio in which the numerator is not a subset of the denominator. It can be interpreted as the likelihood that a case would take place. This is the ratio of cases to non‐cases or p/(1 − p)a |
| Odds ratio | 4 | Odds of the disease in the exposed group divided by the disease odds in the non‐expose groupa |
| Population attributable fraction | 1 | Analogous to Attributable Fraction BUT reflects the effect of the disease in the entire population (rather than in the exposed group)a |
| Population attributable risk | 1 | Difference in risk between two groups BUT focus on increase in risk of disease, in the entire population, attributable to the exposurea |
| Prevalence | 1 | Proportion or percentage of cases in the population at a specific point in time. Eg. cases/populationa |
| Proportion | 1 | Ratio in which the numerator is a subset of the denominatora |
| R 0 (Basic reproductive ratio) | 1 | Average number of secondary cases produced by one infectious individual in completely susceptible population |
| Regression techniques | 1 | E.g. Generalised linear models |
| Relative risk/risk ratio | 4 | Ratio of the risk of disease in the exposed group to the risk of disease in the non‐expose group. Also referred to as ‘Risk Ratio’a |
| Secondary attack rates | 2 |
Number of cases MINUS the initial case(s)a It describes the “infectiousness” (or ease of spread) of living agents |
| Simulation techniques | 8 | The implementation of virtual (computer) sampling from a parametric or empirical distribution in order to estimate the parameter of interest (a probability or a quantity) and its uncertainty/variability e.g. SIR models. These techniques are normally used for predictive purposes |
| Smoothing (kernel) methods | 1 | Techniques used in spatial analysis which convert large sets of points into a density surface |
| Transmission kernel | 1 | The transmission kernel describes the risk of transmission as a function of distance between an infectious and a susceptible holding |
| Transmission rate | 1 | The number of new cases produced by one infectious individual per unit of time |
a
Dohoo, Martin, Stryhn; 2010. Veterinary epidemiological Research – 2nd edition.