Weekly U.S. Influenza Surveillance Report

Angie Szumlinski Health

Key Updates for Week 20, ending May 22, 2021

Seasonal influenza activity in the United States remains lower than usual for this time of year.


Clinical Labs – The percentage of respiratory specimens testing positive for influenza at clinical laboratories is 0.1% this week.

Public Health Labs – The number of influenza positive specimens reported by public health labs remains unusually low.


Outpatient Illness: ILINet

The percentage of patient visits to a health care provider for influenza like illness (ILI) in week 20 was 1.3%, remaining stable compared to week 19. Nationally, ILI remains below the national baseline of 2.6%. ILI surveillance may be impacted by the COVID-19 pandemic and should be interpreted with caution.

Hospitalizations – FluSurv-NET sites reported a cumulative hospitalization rate of 0.8 per 100,000 population, which is about one-tenth the rate of the low-severity 2011-12 seasion.

NCHS Mortality – 9.5% of deaths were attributed to pneumonia, influenza, or COVID-19 (PIC). This is above the epidemic threshold of 63%. Currently, the majority of PIC deaths are due to COVID-19.

Key Points

  • Flu activity is unusually low at this time.
  • One human infection with an influenza A (H1N2) variant (A(H1N2)v) was reported this week. This is the first influenza A(H1N2)v virus identified in the United States in 2021.
  • An annual flu vaccine is the best way to protect against flue and its potentially serious complications.
  • There are also flu antiviral drugs that can be used to treat flu illness.

Remember, the flu is still around; we might not have been exposed due to the CDC recommendations for limiting crowds, social distancing, masking, etc. however it is alive and well. The CDC expects these numbers to change throughout late summer and early fall.

Stay well and stay tuned!