Public Health Surveillance refers to the ongoing systematic collection, analysis and interpretation of data about the health of a population. It involves monitoring disease patterns and trends, as well as tracking exposures to potential health hazards in order to identify and prevent outbreaks of infectious diseases or other health threats. Surveillance systems can include various sources such as hospitals, clinics, laboratories, vital statistics records, and other data collection mechanisms. The information gathered through surveillance is used by public health officials to make informed decisions about disease prevention, outbreak response, and health policy development.