Surveillance of influenza A(H1N1)v will evolve in response to the epidemiological situation. Currently, it focuses on comprehensive case finding to prevent the spread of the virus within the country through the rapid implementation of control measures around confirmed cases. This case-based surveillance includes the reporting of imported cases and clusters of cases. As soon as cluster cases extend beyond close contacts, local surveillance will be implemented in the affected area to detect early community spread of the virus before indicators from sentinel surveillance systems are impacted. When the number of cases becomes too high, individual case surveillance will be replaced by population-based surveillance and will cease. Ultimately, only sentinel surveillance will remain in place for a portion of the population—a surveillance system used annually to track seasonal influenza outbreaks and involving the monitoring of cases, hospitalizations, and deaths through various networks. (R.A.)