> See also: > - [[Vaccines]] # Epidemiology > [!important] Disease vs Disorder > The two will almost always be accepted interchangeable, however these are the formal definitions to help ease your sanity: > - A disorder is a group of symptoms that disrupts your normal body fucntiosn but does not have a known cause (A further subset of “Syndrome”) > - A **Systemic epidemiology** is focused on social and ecological factors that influence the development of emerging diseases **Disease incidence** is a measure of the number of *new cases* over a defined time period as a proportion of the total population A common-source epidemic results from a single, contaminated source such as food or water - Rapid increase followed by less-repid decrease ## Healthcare-Associated Infections Healthcare-associated, or **nosocomial infections**, result from infections acquired by patients while in a hospital or other clincal care facility. Onset of the disease can potentially occur after a patient has been discharged. Infections that are already incubating when patients are admitted to a hospital are not nosocomial infections and are instead community acquired. ## Preventing & Controlling Epidemics