#16,894
Even though it is late July, and flu activity (at least in humans) has declined markedly in the Northern Hemisphere, influenza remains a serious concern for public health agencies - both here in the United States - and around the world.While the HPAI H5N1 clade 2.3.4.4b virus causing our North American and European epizootic remains primarily a threat to avian species - it has caused at least two human infections - and continues to spill over - often with severe neurological manifestations - to land and marine mammals.
Maine: Seal Deaths Linked To Avian H5N1
Two States (Michigan & Minnesota) Report HPAI Infection In Wild Foxes
Ontario: CWHC Reports HPAI H5 Infection With Severe Neurological Signs In Wild Foxes (Vulpes vulpes)
Netherlands DWHC Reports another Mammal (Polecat) Infected With H5N1
CDC EID Journal: Encephalitis and Death in Wild Mammals at An Animal Rehab Center From HPAI H5N8 - UK)
To this surge in avian flu viruses we can also add swine variant viruses, which continue to evolve and spread in swine herds round the world (see EID Journal: Zoonotic Threat of G4 Genotype Eurasian Avian-Like Swine Influenza A(H1N1) Viruses, China, 2020), occasionally spilling over into humans.
At a time when (novel and seasonal) influenza threats are rising, surveillance and reporting from many countries has declined. For some countries, this can be attributed to a lack of resources and the demands of the COVID pandemic, but for others, it may be rooted more in local economic and political interests.
Between the `noise' generated by COVID, and reductions in surveillance and reporting, I'm hard pressed to think of a time in my last 17 years of blogging when our ability to see emerging threats - particularly from China, Russia, the Middle East, and much of Asia and Africa - has been this low.
Influenza is notoriously unpredictable, and we've thought ourselves to be `on the brink' before - with avian H5N1 and H7N9, and even swine variant flu - and those threats eventually receded. Maybe we'll get lucky again.
But with so many viruses in motion, and our limited visibility around the world, it makes sense to stay vigilant.
All of which brings us to a new report in this week's MMWR, which examines the atypical flu activity we've seen and addresses growing concerns over novel H5N1 and swine variant flu viruses.
I've only posted some excerpts from a much longer report, so follow the link to read it in its entirety.
Influenza Activity and Composition of the 2022–23 Influenza Vaccine — United States, 2021–22 Season
Weekly / July 22, 2022 / 71(29);913–919
Angiezel Merced-Morales, MPH1,*; Peter Daly, MPH1,*; Anwar Isa Abd Elal1; Noreen Ajayi, MPH1; Ekow Annan, MPH1; Alicia Budd, MPH1; John Barnes, PhD1; Arielle Colon, MPH1; Charisse N. Cummings, MPH1; A. Danielle Iuliano, PhD1; Juliana DaSilva, MA1; Nick Dempster, MPH1; Shikha Garg, MD1; Larisa Gubareva, PhD1; Daneisha Hawkins, MPH1; Amanda Howa, MPH1; Stacy Huang, MPH1; Marie Kirby, PhD1; Krista Kniss, MPH1; Rebecca Kondor, PhD1; Jimma Liddell1; Shunte Moon, PhD1; Ha T. Nguyen1; Alissa O’Halloran, MSPH1; Catherine Smith, MS1; Thomas Stark, PhD1; Katie Tastad, MPH1; Dawud Ujamaa, MS1; Dave E. Wentworth, PhD1; Alicia M. Fry, MD1; Vivien G. Dugan, PhD1; Lynnette Brammer, MPH1 (View author affiliations)View suggested citation
Summary
What is already known about this topic?
CDC collects, compiles, and analyzes data on U.S. influenza activity and viruses.
What is added by this report?
The severity of the 2021–22 influenza season was low, with two waves of influenza A activity. Influenza activity continued from October 2021 through mid-June 2022, with A(H3N2) viruses predominating throughout the season. This report also describes the composition of the Northern Hemisphere 2022–23 influenza vaccine.
What are the implications for public health practice?
Because of the atypical timing and duration of influenza activity, providers and patients should consider influenza infection as a cause of respiratory illness. Testing for seasonal influenza and monitoring for novel viruses, especially avian A(H5N1) and swine viruses, should continue year-round. Receiving a seasonal influenza vaccine each year remains the best way to protect against seasonal influenza and its potentially severe consequences.
Before the emergence of SARS-CoV-2, the virus that causes COVID-19, influenza activity in the United States typically began to increase in the fall and peaked in February. During the 2021–22 season, influenza activity began to increase in November and remained elevated until mid-June, featuring two distinct waves, with A(H3N2) viruses predominating for the entire season. This report summarizes influenza activity during October 3, 2021–June 11, 2022, in the United States and describes the composition of the Northern Hemisphere 2022–23 influenza vaccine. Although influenza activity is decreasing and circulation during summer is typically low, remaining vigilant for influenza infections, performing testing for seasonal influenza viruses, and monitoring for novel influenza A virus infections are important. An outbreak of highly pathogenic avian influenza A(H5N1) is ongoing; health care providers and persons with exposure to sick or infected birds should remain vigilant for onset of symptoms consistent with influenza. Receiving a seasonal influenza vaccine each year remains the best way to protect against seasonal influenza and its potentially severe consequences.
The United States influenza surveillance system is a collaborative effort between CDC and its many partners in state, local, and territorial health departments, public health and clinical laboratories, vital statistics offices, health care providers, hospitals, clinics, emergency departments, and long-term care facilities. This report is a summary of the 2021–22 influenza season. This report was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.†
(SNIP)
Novel Influenza A
Novel influenza viruses are influenza A virus subtypes that are different from currently circulating human seasonal influenza H1 and H3 viruses. During the 2021–22 influenza season, four novel influenza A viruses were detected in humans. Three were variant viruses (i.e., a swine influenza virus identified in a person and designated with a “v”); one A(H1N2)v virus was identified in a person in California, one A(H3N2)v in a person in Ohio, and one A(H1)v in a person in Oklahoma. One avian A(H5N1) virus was identified in a person in Colorado who was exposed to birds infected with highly pathogenic avian influenza A(H5N1). The A(H5N1) identification was the first positive test result for avian influenza A(H5) virus in a human in the United States (1).
(SNIP)
Composition of the 2022–23 Influenza Vaccines
Vaccine strains for the 2022–23 influenza vaccines were selected by the Food and Drug Administration’s Vaccines and Related Biologic Products Advisory Committee based on WHO’s recommended Northern Hemisphere 2022–23 influenza vaccine composition. No changes were made to the A(H1N1)pdm09 or the B/Yamagata egg-based, cell-based, or recombinant vaccine recommended components. The recommended A(H3N2) component was changed to an A/Darwin/9/2021 (H3N2)–like virus for egg-based vaccines and an A/Darwin/6/2021 (H3N2)–like virus for cell-based or recombinant vaccines. The B/Victoria component recommendation was changed to a B/Austria/1359417/2021–like virus (3,4). The clade and subclade for the recommended vaccine strains were 6b.1A.5a.2 for A(H1N1)pdm09, 3C.2a1b.2a.2 for A(H3N2), V1A.3a.2 for B/Victoria, and Y3 for B/Yamagata.
(SNIP)
Despite decreasing influenza activity in recent weeks, maintaining vigilance for influenza virus infections throughout the summer is important. Sporadic seasonal influenza virus infections and novel influenza A virus infections associated with exposure to swine during animal exhibitions are often reported during summer months (6). In addition, an ongoing outbreak of highly pathogenic avian influenza A(H5N1) virus among birds during the 2021–22 season underscores the importance that providers and persons with exposure to sick or infected birds remain attentive to any new symptoms that could be consistent with influenza virus infection (7).
Patients with suspected novel influenza A virus should isolate at home away from household members and refrain from going to work or school until they are proven to not be infected or have recovered from their illness. Specimens from patients with suspected novel influenza A virus infection should be collected and referred to state public health departments for testing, and treatment with influenza antiviral medications should be initiated immediately. Treatment is recommended and should be initiated as soon as possible for patients with confirmed or suspected seasonal or swine influenza virus infection who have severe, complicated, or progressive illness; who require hospitalization; or who are at increased risk for influenza-associated complications (8).
Influenza antiviral drugs are approved by the Food and Drug Administration for treatment of acute uncomplicated influenza within 2 days of illness onset and are recommended for use in the United States during the 2021–22 season. For persons aged ≥6 months, receiving a seasonal influenza vaccine each year remains the best way to protect against seasonal influenza and its potentially severe consequences.
Influenza surveillance reports for the United States are posted online weekly (https://www.cdc.gov/flu/weekly). Additional information regarding influenza viruses, surveillance, vaccines, antiviral medications, and novel influenza A infections in humans is available online (https://www.cdc.gov/flu).
