Monday, November 29, 2021

CDC FluView Week 46: Another Novel Flu (H1) Variant (Oklahoma) While Seasonal Flu Slowly Climbs

Week #46 ILI Activity - Credit FluView

The CDC  published a belated FluView report  today due to the Thanksgiving Holiday, which shows flu activity - while still low - continues to rise in parts of the United States.  

Over the past few weeks we've been following outbreaks of influenza at several Universities which led to the CDC issuing a HAN Advisory last week (see CDC HAN # 00458 : Increasing Seasonal Influenza A (H3N2) Activity).

The CDC's summary of today's report follows, plus details on the 2nd Novel virus detection of the 2021-2022 flu season.  I'll have a postscript after the break.

Key Points
  • Influenza activity remains low nationally, but in recent weeks both laboratory-confirmed influenza detections and outpatient visits due to ILI are increasing.
  • The number of influenza viruses detected by clinical and public health labs has increased in recent weeks. The majority of viruses detected are A(H3N2). About 89% have occurred among children and young adults aged 5-24 years.
  • The percentage of outpatient visits due to ILI has trended upwards in recent weeks but remains below baseline.
  • An annual flu vaccine is the best way to protect against flu and its potentially serious complications. CDC recommends everyone 6 months and older get a flu vaccine.
  • As of November 19, 2021, 166.9M doses of flu vaccine have been distributed in the US.
  • Flu vaccines are available at many different locations including pharmacies and health departments. Visit to find a flu vaccine near you.
  • There also are flu antiviral drugs that can be used to treat flu illness.

Novel Influenza A Virus

One human infection with a novel influenza A virus (H1, neuraminidase result pending) was reported by Oklahoma. The infection occurred in an adult ≥ 18 years of age. The patient was hospitalized for an unrelated illness and has since been discharged. The patient had direct swine contact at home and at an agricultural event prior to specimen collection. No ongoing human-to-human transmission has been identified associated with this case.

This is the second human infection with a novel influenza A virus that has occurred during the 2021-22 influenza season. The previous infection was an influenza A (H3N2) variant reported by Ohio that occurred in a child < 18 years of age.

When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant influenza virus”. Most human infections with variant influenza viruses occur following close proximity to swine, but human-to-human transmission can occur. It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person.
Early identification and investigation of human infections with novel influenza A viruses are critical so that the risk of infection can be more fully understood and appropriate public health measures can be taken. Additional information on influenza in swine, variant influenza virus infection in humans, and strategies to interact safely with swine can be found at Additional information regarding human infections with novel influenza A viruses can be found at

Three weeks ago the CDC announced Three More Novel Influenza Infections (H1N1v & H1N2v) Reported, with two of those occurring during the 2020-2021 flu season. We've also seen sporadic human infections with swine variant viruses (H1N1v, H1N2v, H3N2v) around the world, with recent cases reported in FranceTaiwanCanadaBrazil, Germany, and the Netherlands.

For now, sporadic jumps of swine variant influenza from pigs to humans pose only a minor public health risk, but they do have some pandemic potential (as we saw in 2009).

Of greater concern is the return of seasonal flu, which may co-circulate with both the Delta and Omicron Coronavirus variants this winter  And while the data is limited, coinfection with COVID and flu has been linked to a higher mortality risk (see PHE Study: Co-Infection With COVID-19 & Seasonal Influenza) than either standalone infection.

While no one can predict what lies ahead, but given the news of the day, I'm glad I'm going into this winter fully vaccinated against both flu and COVID. 

And I sincerely urge others to do the same. As we could be facing a challenging winter.