National report: During week 46 (November 11-17, 2001), 5 specimens tested by the World Health Organization (WHO) and National Respiratory and Enteric Virus Surveillance System (NREVSS) collaborating laboratories across the United States were positive for influenza. Since September 30, a total of 6,171 specimens for influenza viruses have been tested and 50 (0.8%) were positive. Of the 50 isolates identified, 48 were influenza A viruses and 2 were influenza B viruses. Twenty of the influenza A viruses were subtyped, all were influenza A (H3N2). Influenza A isolates have been identified in Alaska, Arizona, Florida, Hawaii, Kentucky, Louisiana, New York, North Carolina, Texas, Utah, Washington and Wisconsin. The influenza B isolates were identified in Michigan and Texas.  The proportion of patient visits to sentinel physicians for influenza-like illness (ILI) overall was 1.2%, which is less than the national baseline of 1.9%. The proportion of deaths attributed to pneumonia and influenza as reported by the vital statistics offices of 122 U.S. cities was 6.6% during week 46. This percentage is below the epidemic threshold of 7.3% for this time. Four state and territorial health departments (Alaska, Colorado, New York and Ohio) reported regional influenza activity (defined as influenza outbreaks in one or several counties with < 50% of the state’s combined population). Sporadic activity was reported from 19 states (Alabama, Arizona, California, Delaware, Florida, Georgia, Indiana, Iowa, Kansas, Maine, Michigan, Missouri, Nevada, New Mexico, North Dakota, Tennessee, Utah, West Virginia, and Wyoming), 24 states reported no influenza activity.