Active surveillance is a research area in healthcare and epidemiology that involves ongoing monitoring and tracking of individuals who are at risk for a particular disease or condition, but who do not currently have any symptoms. This approach is often used in situations where the natural history of a disease is not well understood, or where treatment options are limited or risky. Active surveillance typically involves regular check-ups, screenings, and tests to detect any early signs or changes in health status, in order to facilitate early intervention or treatment if necessary. This method is particularly useful for monitoring infectious diseases, chronic conditions, and certain types of cancers, as it can help healthcare providers to identify and respond to potential outbreaks or worsening of a disease before it becomes more serious. Overall, active surveillance is a proactive and preventative approach to healthcare that aims to improve outcomes for individuals at risk of developing certain health conditions. It can be a valuable tool in disease prevention, management, and control.