Influenza Surveillance and ACIP Influenza Update – Alicia Budd (CDC)
Alicia provided highlights of the influenza surveillance report from week 16, ending April 21, 2018. All indicators are continuing to show a decline in flu activity levels.
The percentage of respiratory specimens testing positive for influenza in clinical laboratories was 8.9%. Positive specimens for both influenza A and B are considerably lower than peak levels and continue to decline. Data for week 16 from public health laboratories continues to show influenza B is the most predominantly reported virus. The vast majority of these B viruses are of the Yamagata lineage. Of the influenza A viruses reported for the season overall, 41% were H1. However, for the season as a whole, influenza H3N2 remains the predominant virus.
Specimens characterized since May continue to be antigenically and genetically similar to the reference virus for this season’s vaccine. Almost all H1, H3, and B Yamagata viruses are similar to their respective cell-grown viruses. However, the egg-grown viruses have a lower similarity to the vaccine virus for H3. In addition, approximately 75% of the B Victoria viruses have a particular genetic change and amino acid deletion that affects their antigenic similarity to the vaccine.
A total of ten (10) H1 specimens have been found to be antiviral resistant this season. This is still quite low, occurring with just over 1% of the H1 specimens tested. No antiviral resistance has been detected for H3 or B viruses.
Nationwide, influenza-like illness (ILI) activity has continued to decline during week 16, with the reported 1.7% falling well below the 2.2% baseline. Nine of the ten HHS regions reported being below baseline levels for ILI activity. ILI information also is available on a state level, with activity summarized as high, moderate, low, or minimal. Last week, 3 states reported high ILI activity, while the remaining 47 states reported minimal ILI activity.
Information from the Influenza Hospitalization Surveillance Network (FluSurv-NET) indicates an overall hospitalization rate of 105 per 100,000 population. The highest rate was among adults age >65 years, followed by adults age 50–64.
The percent of deaths attributed to pneumonia and influenza (P&I) during week 16 declined to 6.7%, which fell below the epidemic threshold for the first time this week.
Four (4) new influenza-associated pediatric deaths were reported during week 16. For the 2017–2018 season, the total number of reported pediatric deaths is 160. The split between viruses remains relatively stable, with 37% of these deaths were associated with influenza B viruses and 63% with influenza A viruses. Among the influenza A viruses with subtype information available, 46% were H1 viruses and 53% were H3 viruses.
In terms of geographic spread of influenza within a state (characterized as widespread, regional, local, sporadic, or no activity) as reported by state and territorial epidemiologists, 4 states reported widespread activity; 9 states reported regional activity; 25 states reported local activity; 10 states reported sporadic activity; and 2 states reported no influenza activity.
Announcements – L.J Tan (IAC)
- CDC/Emory University Symposium – On May 7 CDC and the Emory University Rollins School of Public Health will host a one-day symposium, 100 Years of Influenza Pandemics and Practice: 1918-2018, This event will feature experts from academia and government will convene to discuss and debate current pandemic influenza threats, and the future of pandemic preparedness and influenza prevention and control. The event is free, but registration is required in order to attend the symposium. Presentations also will be live-streamed for persons who cannot attend in person.
- Summit Meeting and NIC – L.J reminded partners to register for the annual face-to-face Summit meeting on May 17–18. This will take place immediately after the National Immunization Conference (NIC). It is helpful to have everyone registered so that we can appropriately plan for meeting room size and the Awards Luncheon. Individuals needing the password to register for the meeting should contact L.J Tan.
- Next Summit calls – Due to the upcoming face-to-face meeting, the Summit calls scheduled for May 10 and May 17 have been CANCELLED.