Attack rate
Encyclopedia
In epidemiology
, an attack rate is the cumulative incidence
of infection
in a group of people observed over a period of time during an epidemic
, usually in relation to foodborne illness
.
The term is defined as the number of exposed persons infected with the disease
divided by the total number of exposed persons.
It is measured from the beginning of an outbreak
to the end of the outbreak
. The term should probably not be described as a rate because its time dimension is uncertain . For this reason, it is often referred to as an attack ratio.
For instance, if there are 70 people taken ill out of 98 in an outbreak, the attack rate is
or about 71.4%.
Epidemiology
Epidemiology is the study of health-event, health-characteristic, or health-determinant patterns in a population. It is the cornerstone method of public health research, and helps inform policy decisions and evidence-based medicine by identifying risk factors for disease and targets for preventive...
, an attack rate is the cumulative incidence
Cumulative incidence
Cumulative incidence or incidence proportion is a measure of frequency, as in epidemiology, where it is a measure of disease frequency during a period of time...
of infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
in a group of people observed over a period of time during an epidemic
Epidemic
In epidemiology, an epidemic , occurs when new cases of a certain disease, in a given human population, and during a given period, substantially exceed what is expected based on recent experience...
, usually in relation to foodborne illness
Foodborne illness
Foodborne illness is any illness resulting from the consumption of contaminated food, pathogenic bacteria, viruses, or parasites that contaminate food, as well as chemical or natural toxins such as poisonous mushrooms.-Causes:Foodborne illness usually arises from improper handling, preparation, or...
.
The term is defined as the number of exposed persons infected with the disease
Disease
A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...
divided by the total number of exposed persons.
It is measured from the beginning of an outbreak
Outbreak
Outbreak is a term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected at a particular time and place. It may affect a small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious...
to the end of the outbreak
Outbreak
Outbreak is a term used in epidemiology to describe an occurrence of disease greater than would otherwise be expected at a particular time and place. It may affect a small and localized group or impact upon thousands of people across an entire continent. Two linked cases of a rare infectious...
. The term should probably not be described as a rate because its time dimension is uncertain . For this reason, it is often referred to as an attack ratio.
For instance, if there are 70 people taken ill out of 98 in an outbreak, the attack rate is
or about 71.4%.