December 14, 2017

Influenza Surveillance Update – Alicia Budd (CDC)

Alicia provided highlights of the influenza surveillance report from week 48, ending on December 2, 2017. Overall, influenza activity is continuing to increase throughout the country.

The percentage of respiratory specimens testing positive for influenza in clinical laboratories was 6.7%. This is down slightly from the 6.9% positives reported during the previous week. However, this is likely due to the effect of delayed holiday reporting. Over 11,000 specimens have been tested at public health laboratories. The majority of these specimens (87%) were influenza A, Of these influenza A specimens, 91% were were H3. Of the influenza B viruses for which lineage information was available, 95% were B Yamagata.

Specimens characterized since May have been antigenically and genetically similar to the reference virus for this season’s vaccine. One caller asked if this is true for both egg-based and cell-based vaccines. Alicia referenced last week’s MMWR article, Update: Influenza Activity – United States, October 1-November 25, 2017. Antigenic changes in the viruses are measured against cell-grown viruses because CDC is trying to determine if the viruses are drifting from what we know is circulating. However, the similarity between reference vaccine viruses and circulating viruses also is compared for egg-grown viruses. The percentage similar to egg-grown is a little lower than cell-grown, with 98% of H3 viruses similar to cell-propogated vaccine viruses and 70% similar to egg-propogated viruses. From a communications standpoint, it is important to clarify this information in light of the news about low (10%) vaccine effectiveness in Australia. Alicia pointed out that FAQs are available on the CDC website to help deal with this question. In short, the U.S. is not seeing a significant decrease in vaccine effectiveness such as found in the E, the information from Australia. CDC will continue to monitor this situation closely. There has been no antiviral resistance detected to date.

Nationwide, influenza-like illness (ILI) activity was at 2.3%, up slightly from the 2.2% reported in the previous week. During week 48, four HHS regions (Regions 1, 4, 6, and 7) were either at or above their region-specific baselines. ILI information also is available on a state level, with activity summarized as minimal, low, moderate, or high. Last week, 38 states and New York City reported minimal ILI activity, 6 states and the District of Columbia reported low ILI activity, 3 states (Georgia, Hawaii, and Texas) and Puerto Rico reported moderate ILI activity, and 3 states (Louisiana, Mississippi, and South Carolina) reported high ILI activity.

Hospitalization data from FluServe-NET indicates a preliminary cumulative hospitalization rate for all age groups of 3.0/100,000. The highest rate (11.5/100,000) is in persons age 65 years and older, followed by adults 50–64 years (3.3/100,000) and children 0–4 years (2.7/100,000).

Based on reports from the National Center for Health Statistics (NCHS) surveillance system available for the week ending November 18, 5.7% of deaths were due to pneumonia and influenza (P&I). This percentage is below the epidemic threshold of 6.6% for the week.

Two influenza-associated pediatric deaths were reported during week 48. One was associated with a H3 virus infection, while the other was associated with B Yamagata infection. For the 2017–2018 season, the total number of reported pediatric deaths now stands at seven.

In terms of geographic spread of influenza within a state (characterized as regional, local, sporadic, or no activity) as reported by state and territorial epidemiologists, 7 states reported sporadic activity, 18 reported local activity, 18 reported regional activity, and 7 reported widespread activity. The number of states at regional or widespread increased from week 47 (14 states) to week 48 (25 states, indicating increased geographic spread of infection.

Announcements – L.J Tan (IAC)
    • Upcoming Summit Calls – L.J announced that, due to the upcoming holidays, the routine Summit calls will not be held for the next three weeks. (Per the routine schedule, calls would have been held on December 21, December 28, and January 4.) The next Summit call is now scheduled for January 11 at 3 p.m. ET.


    • National Immunization Conference (NIC) Abstracts – Amy Parker Fiebelkorn reminded callers that we are rapidly approaching the December 31 deadline for submission of abstracts to NIC. The same abstracts may be submitted to the Summit site when it becomes available online. The registration page should be launched soon after the beginning of the year.
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