The percentage of people visiting the doctor for influenza-like illness (ILI) last week jumped from 3.3% to 3.8%, a sign that the flu season is in full effect across much of the United States, according to today's weekly FluView update from the Centers for Disease Control and Prevention (CDC).
All 10 geographic regions of the country recorded high ILI activity for the fourth week of 2019.
New York City and 23 states reported high ILI, compared with 18 states the previous week. Puerto Rico and 10 states are experiencing moderate ILI, and the District of Columbia and 13 states are reporting low ILI.
Widespread influenza activity was reported in 45 states, up from 36 states in the previous week. Only Colorado, Indiana, and West Virginia reported regional activity, and both Alaska and Hawaii recorded local activity.
Hospitalizations up in elderly
The overall hospitalization rate last week for flu was 15.3 per 100,000 population, up from 14.8 per 100,000 population the week before. The highest rate of hospitalization was among adults older than 65 (39.8 per 100,000 population), the CDC said, followed by children ages 0 to 4 (27.3 per 100,000 population).
The rate among elderly people was 38.3 per 100,000 population during the previous week. A total of 93.0% of hospitalizations were associated with influenza A virus last week, and 5.7% with influenza B virus.
Influenza A has dominated this flu season, representing 98.7% of lab specimens tested last week. Of those, 75.2% are the 2009 H1N1 strain, and 24.8% are the H3N2 strain. The CDC said last week that H3N2 activity is concentrated in the Southeast.
The CDC also noted that the proportion of deaths attributed to pneumonia and influenza (P&I) was 7.2% last week, breaching the national threshold of 7.0%.
"P&I has been at or above the epidemic threshold for three consecutive weeks so far this season, however, hospitalization rates remain relatively low compared with last season," the CDC said in its summary of the FluView report.
Two more pediatric deaths were recording, bringing the season's total to 24. Both deaths occurred during the third week of January and were attributed to influenza A infections for which no sub-typing was performed.
Feb 1 CDC FluView
Feb 1 CDC FluView summary