April 12, 2018

April 12, 2018

Influenza Surveillance and ACIP Influenza Update – Alicia Budd (CDC)

Alicia provided highlights of the influenza surveillance report from week 13, ending March 31, 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 15.4%. This overall positive level has been relatively stable for the last four weeks. Positive specimens for both influenza A and B are considerably lower than peak levels, but also continue to hold relatively level. Data from public health laboratories indicates influenza B accounted for almost two-thirds of the reports from those facilities. For the season as a whole, influenza H3N2 is the predominant virus. During week 13, almost 35% of the positive influenza A specimens were H1.

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 for H3. In addition, a growing subset (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 nine (9) 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 was at 2.4%. This is the nineteenth consecutive week we have been above the baseline of 2.2%. Three HHS regions (Regions 2, 6, and 8) are now below baseline levels for ILI activity, while the other 7 regions remain above baseline. ILI information also is available on a state level, with activity summarized as high, moderate, low, or minimal. Last week, 2 states (Alaska and Virginia) reported high ILI activity; 8 states reported moderate ILI activity; 12 states and New York City reported low ILI activity; and 28 states, the District of Columbia, and Puerto Rico reported minimal ILI activity.

Information from the Influenza Hospitalization Surveillance Network (FluSurv-NET) indicates an overall hospitalization rate of 99.9 per 100,000 population. The highest rate (429.4 per 100,000) was among adults age >65 years, followed by adults age 50–64 (108.7 per 100,000 population) and children age 0–4 (71.2 per 100,000).

The percent of deaths attributed to pneumonia and influenza (P&I) during week 13 declined to 7.1%, which is below the epidemic threshold. This is the first week P&I has been below the threshold in 12 weeks.

Five (5) new influenza-associated pediatric deaths were reported during week 13. One death was associated with an influenza A(H3) virus and occurred during week 13. Two deaths were associated with an influenza A virus for which subtyping was not performed and occurred during weeks 9 and 12. Two deaths were associated with an influenza B virus and occurred during weeks 12 and 13. For the 2017–2018 season, the total number of reported pediatric deaths is 142. 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, 11 states reported widespread activity; 26 states, Guam, and Puerto Rico reported regional activity; 10 states and the District of Columbia reported local activity; 3 states and the Virgin Islands reported sporadic activity.

Announcements – Amy Parker Fiebelkorn (CDC)

Amy reminded partners to register for the National Immunization Conference (NIC) to be held on May 15–17 in Atlanta, Georgia. The annual Summit meeting will take place immediately after NIC on May 17–18. Registration for the Summit meeting is available online. Individuals needing the password to register for the meeting should contact L.J Tan.

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