All data are preliminary and may change as more reports are received.During week 51 (December 18-24, 2016), influenza activity increased in the United States.\u2022 Viral Surveillance: The most frequently identified influenza virus subtype reported by public health laboratories during week 51 was influenza A (H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories increased.\u2022 Novel Influenza A Virus: One human infection with a novel influenza A virus was reported.\u2022 Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was below the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillan...