Influenza Surveillance Update – Alicia Budd (CDC)
Alicia provided an update on influenza activity reported for week 9, ending March 2, 2019. Influenza activity continues to remain elevated. Several indicators suggest we possibly have peaked for the 2018–2019 influenza season.
For the week, 26.1% of specimens sent to clinical laboratories tested positive for influenza. This is a slight increase from the percentage reported during the previous week. Influenza A (H1) remains the predominant strain reported, but the proportion of H3 reports is increasing. Looking at reports from the last three weeks, 5 regions (Regions 2, 4, 6, 7, and 8) have been H3 predominant. Region 4 is the only region that has been H3 predominant for the entire season. The amount of reported influenza B circulating viruses continues to remain remarkably low.
During this season, more than 1,400 viruses have been genetically or antigenically characterized. All of the H1 viruses are the 6B1 clade, and 99% of the antigenically characterized H1 viruses were similar to the cell-propagated vaccine reference virus. Multiple clades and subclades of the H3 virus are co-circulating, with the 3C3a subclade continuing to increase. At 59%, this is the predominant subclade in the U.S. this season. Sixty-two percent (62%) of the H3s are antigenically similar to the cell-grown reference virus representing the vaccine strain. Most of the H3s that had low similarity to the cell-grown reference virus belong to clade 3C3a.
All of the Influenza B Yamagata viruses tested have belonged to the Y3 clade and are similar to the cell-grown vaccine virus. Co-circulation of several Victoria viruses is occurring, but the majority (66%) belong to the V1A.1 clade. More than 1,400 viruses have been tested for resistance to oseltamivir, peramivir, and zanamivir. All viruses tested showed susceptibility to zanamivir, and more than 99% displayed susceptibility to oseltamivir and peramivir. Four H1 specimens have been found to have reduced or highly reduced inhibition by oseltamivir and peramivir.
Outpatient visits for influenza-like illness (ILI) declined during the week to 4.7%. This is the second week in a row in which a decline has been experienced. Despite this decline, ILI activity is still elevated and has been at or above baseline nationally for 13 consecutive weeks. All 10 surveillance regions were above their region-specific baselines. However, 4 regions (regions 1,2,4, and 6) have seen ILI decline for at least 2 weeks in a row. On a state level, 33 states experienced high ILI levels, 7 states reported moderate activity, and the remaining 11 states were at low or minimal activity levels.
Cumulative reports to FluSurv-NET this season indicate a rate of 36.6/100,000 lab-confirmed influenza hospitalizations. Highest hospitalization rates were seen in persons >65 years at 108/100,000, followed by the 0–4 age group at approximately 49/100,000.
The percent of deaths reported due to pneumonia and influenza (P&I) was 7.5% during the week ending February 23, slightly above the epidemic threshold for this week.
Sixty-four (64) influenza-associated pediatric deaths were reported to CDC this season. Of these 60 were associated with influenza A virus infections, 3 with an influenza B virus infection, and 1 with an influenza virus that wasn’t typed. Eighty-three percent (83%) of the A viruses with subtype information available were H1.
For the geographic spread of influenza during the week, 48 states and Puerto Rico reported widespread activity. Two (2) states and the District of Columbia reported regional activity, and the Virgin Islands reported sporadic activity.
For the preliminary influenza burden reports released, an estimated 22.8–26.3 million persons have been ill with flu. Approximately half of those persons have received medical care, and 289,000–347,000 were hospitalized. An estimated 18.9–31.2 persons have died.
Other Items – L.J Tan (IAC)
- NFID Annual Conference on Vaccinology Research – The National Foundation for Infectious Diseases (NFID) is holding its 2019 Annual Conference on Vaccinology Research (ACVR) on April 3–5 in Baltimore, MD. Discussions at the conference will include the role of vaccines in terms of preventing existing and emerging infectious diseases, working against antimicrobial resistance, and other similar topics. Speakers have been confirmed from the Bill and Melinda Gates Foundation, CDC, FDA, and NIH. Additional information and registration details are available online.
- Trust for America’s Health (TAH) Congressional Briefing – TAH is releasing its annual report on readiness, Ready or Not? The briefing will occur on March 18 at 12:30 pm.
- NFID Webinar – NFID’s webinar, Updates on the February 2019 ACIP Meeting, will be held on March 19 at noon. Dr. William Schaffner, NFID’s Medical Director, and Amanda Cohn, ACIP’s Executive Secretary, will provide summaries of the meeting.
- 2019 Summit In-Person Meeting Information Now Available Online – The 2019 Summit in-person meeting will be held in Atlanta, GA on May 14–16, 2019. Information on registration, submission of poster abstracts, and nominations for the 2019 Immunization Excellence Awards is available on the 2019 National Adult and Influenza Immunization Summit webpage. (Please note that the password to register for this invitation-only meeting is available by contacting L.J Tan.) If possible, please book your room either through the onscreen “pop-up” that appears after you register or later through the email you receive after completing your registration. This not only will give you access to the “preferred rate,” it also will help the Summit meet its lodging contractual agreement with the hotel. The Summit will continue accepting abstracts for poster presentations through March 15.