<prompt> Measures involved in sentinel surveillance include all exceptIdentifying cases free of disabilityIdentifying new cases of infectionIdentifying old cases and new cases of infectionIdentifying missing cases in notification of disease  <response>: Surveillance: Is the ongoing systematic collection and analysis of data and the provision of information which leads to action being taken to prevent and control a disease, usually one of an infectious natureSurveillance is of many types:Passive Surveillance: Data is itself reported to the health system; For e.g., A patient with fever coming on his own to the PHC, CHC, Dispensary, Private Practitioner, HospitalActive Surveillance: Health system seeks out actively the collection of data, i.e., goes out to community to collect data; For e.g., Stool sample collection from home in Polio Program.Sentinel Surveillance: Monitoring of rate of occurrence of specific conditions to assess the stability or change in health levels of a population, It is also the study of disease rates in a specific cohort, geographic area, population subgroup, etc. to estimate trends in larger population; For e.g., Use of health practitioners to monitor trends of a health event in a populationSentinel Surveillance helps in identifying missing cases and supplementing notified cases 