 Public Health Surveillance, Public Health Surveillance Also Epidemiological Surveillance, Clinical Surveillance or Syndromic Surveillance is, according to the World Health Organization who the continuous, systematic collection, analysis and interpretation of health related data needed for the planning, implementation and evaluation of public health practice. Public Health Surveillance may be used to serve as an early warning system for impending public health emergencies, document the impact of an intervention, or track progress towards specified goals, and monitor and clarify the epidemiology of health problems, to allow priorities to be set and to inform public health policy and strategies. Public Health Surveillance Systems can be passive or active. A passive surveillance system consists of the regular, ongoing reporting of diseases and conditions by all health facilities in a given territory. An active surveillance system is one where health facilities are visited and health care providers and medical records are reviewed in order to identify a specific disease or condition. Passive surveillance systems are less time consuming and less expensive to run but risk under reporting of some diseases. Active surveillance systems are most appropriate for epidemics or where disease has been targeted for elimination. Techniques of public health surveillance have been used in particular to study infectious diseases. Many large institutions, such as the COO and the SIRDC, have created databases and modern computer systems. Public health informatics that can track and monitor emerging outbreaks of illnesses such as influenza, SARS, HIV, and even bioterrorism, such as the 2001 anthrax attacks in the United States. Many regions and countries have their own cancer registry, one function of which is to monitor the incidence of cancers to determine the prevalence and possible causes of these illnesses. Other illnesses such as one-time events like stroke and chronic conditions such as diabetes, as well as social problems such as domestic violence, are increasingly being integrated into epidemiologic databases called disease registries that are being used in cost benefit analysis in determining governmental funding for research and prevention. Systems that can automate the process of identifying adverse drug events, are currently being used, and are being compared to traditional written reports of such events. These systems intersect with the field of medical informatics, and are rapidly becoming adapted by hospitals and endorsed by institutions that oversee healthcare providers such as JCEAA chose in the United States. Issues in regard to healthcare improvement are evolving around the surveillance of medication errors within institutions.