CDC: US influenza has reached epidemic levels

During week 5 (January 28-February 3, 2018), influenza activity increased in the United States.

During week 5 (January 28-February 3, 2018), influenza activity increased in the United States.

  • Viral Surveillance:  The most frequently identified influenza virus subtype reported by public health laboratories during week 5 was influenza A(H3). The percentage of respiratory specimens testing positive for influenza in clinical laboratories remained elevated.
  • Pneumonia and Influenza Mortality: The proportion of deaths attributed to pneumonia and influenza (P&I) was above the system-specific epidemic threshold in the National Center for Health Statistics (NCHS) Mortality Surveillance System.
  • Influenza-associated Pediatric Deaths: Ten influenza-associated pediatric deaths were reported.
  • Influenza-associated Hospitalizations: A cumulative rate of 59.9 laboratory-confirmed influenza-associated hospitalizations per 100,000 population was reported.
  • Outpatient Illness Surveillance: The proportion of outpatient visits for influenza-like illness (ILI) was 7.7%, which is above the national baseline of 2.2%. All 10 regions reported ILI at or above region-specific baseline levels. New York City, the District of Columbia, Puerto Rico and 43 states experienced high ILI activity; three states experienced moderate ILI activity; two states experienced low ILI activity; and two states experienced minimal ILI activity.
  • Geographic Spread of Influenza: The geographic spread of influenza in Puerto Rico and 48 states was reported as widespread; two states reported regional activity; the District of Columbia and Guam reported local activity; and the U.S. Virgin Islands reported sporadic activity.


  • CDC warns that influenza continues to be widespread and increasing across the nation, with overall hospitalizations the highest observed and exceeding numbers in 2014-2015.
  • The proportion of people visiting clinicians with influenza-like illness (ILI) has risen to 7.1%, which is 2.1% above the national average and the highest since the 2009 pandemic.

Why this matters

  • The 5 previous influenza seasons have averaged 16 weeks total duration, but CDC cautions clinicians to expect 6-10 additional weeks of illness.
  • Parents/caregivers should be encouraged to contact their providers for children or adolescents with worrisome signs/symptoms (ie, high persisting fever, difficulty breathing/shortness of breath, rapid heartbeat or shallow rapid breathing, significant fatigue or confusion).
  • Because of secondary bacterial pneumonia risk, pneumococcal vaccines in older adults (age, ≥65 years) should be encouraged.

Key points

  • 48 states are reporting widespread influenza activity.
  • Influenza-associated hospitalizations continue to rise; current surveillance figures demonstrate cumulative overall rate of 51.4 hospitalizations per 100,000 persons.
  • Highest hospitalization rate is in adults aged ≥65 years (226.8 per 100,000), followed by adults aged 50-64 years (54.0 per 100,000) and children aged 0-4 years (33.3 per 100,000).
  • CDC is reporting an additional 16 pediatric deaths, bringing this season’s influenza-related deaths to 53.


Source: univadis