Update: influenza activity--United States, 1997-98 season.

In collaboration with the World Health Organization (WHO), its collaborating laboratories, and state and local health departments, CDC conducts surveillance to monitor influenza activity and to detect antigenic changes in the circulating strains of influenza viruses. This report summarizes influenza surveillance in the United States from September 28, 1997, through March 7, 1998, and presents reports of outbreaks in long-term care facilities (LTCFs) in three states and at a military base. The findings indicate that this season has been dominated by influenza A(H3N2) viruses and characterized by a sustained elevation in pneumonia and influenza (P&I)-related deaths.