Influenza Surveillance and ACIP Influenza Update – Alicia Budd (CDC)
Alicia provided highlights of the influenza surveillance report from week 10, ending March 10, 2018. Although we are still at relatively high levels compared to baseline, we have now seen flu activity levels decline for five weeks in a row.
The percentage of respiratory specimens testing positive for influenza in clinical laboratories was 15%. Positive specimens are trending downward for both influenza A and influenza B. Data from public health laboratories indicates influenza B is now predominant. For the season as a whole, influenza H3N2 is the predominant virus. Seven of the 10 surveillance regions reported influenza B as being predominant during week 9.
Specimens characterized since May continue to be antigenically and genetically similar to the reference virus for this season’s vaccine. For H3, H1, and B Yamagata viruses, 98–100% are similar to their respective cell-grown viruses. However, the egg-grown viruses have a lower similarity to the vaccine virus (~64%) for H3. In addition, a subset of the B Victoria viruses have a particular genetic change and amino acid deletion that affects their antigenic similarity to the vaccine. Currently, about 67% of B Victoria viruses have this deletion.
One (1) new H1 specimen was found to be antiviral resistant, bring the season total to 9. This is still quite low, however, occurring with <2% of the H1 specimens tested. No antiviral resistance has been detected for H3 or B viruses.
Nationwide, influenza-like illness (ILI) activity was at 3.3%. Although we are still above the baseline of 2.2%, this is the fifth consecutive week we have seen a decline in this system. All 10 HHS regions now appear to have passed their peak ILI activity. ILI information also is available on a state level, with activity summarized as high, moderate, low, or minimal. Last week, 12 states reported high ILI activity; 13 states reported moderate ILI activity; 14 states and New York City reported low ILI activity; and 11 states reported minimal ILI activity, and data were insufficient to calculate ILI activity for the District of Columbia and Puerto Rico.
Information from the Influenza Hospitalization Surveillance Network (FluSurv-NET) indicates an overall hospitalization rate of 90 per 100,000 population. The highest rate (386 per 100,000) was among adults age >65 years, followed by adults age 50–64 (97 per 100,000 population) and children age 0–4 (65 per 100,000). Overall, the all ages combined rate and all adult rates are at the highest levels ever reported into the system.
Based on reports from the National Center for Health Statistics (NCHS) surveillance system available for the week ending February 24, 8.5% of deaths were due to pneumonia and influenza (P&I). This is the still above epidemic threshold levels, but represents the fifth week in which we have seen a decline in the percentage of deaths attributed to P&I.
Nine (9) new influenza-associated pediatric deaths were reported during week 10. For the 2017–2018 season, the total number of reported pediatric deaths is 128. Approximately one-third of these deaths were associated with influenza B viruses. Of the deaths associated with influenza A viruses, about ½ were associated with H1.
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, 26 states and Puerto Rico reported widespread activity; 18 states and Guam reported regional activity; 5 states and the District of Columbia reported local activity; 1 state reported sporadic activity; and 0 states and the U.S. Virgin Islands reported no influenza activity.
Announcements – L.J Tan (IAC)
L.J reminded partners that they should register for the Summit meeting being held May 17–18 in Atlanta, Georgia. Individuals needing the password to register for the meeting should contact L.J Tan. Persons also are reminded to register for the National Immunization Conference (NIC) to be held immediately prior to the Summit meeting.