March 5, 2020

March 5, 2020

Influenza Surveillance Update – Alicia Budd (CDC)

Alicia provided an update on influenza activity through Week 8, ending on February 22, 2020.  While influenza activity remains high, it has decreased for the second consecutive week.  Indicators of influenza severity are moderate to low overall, but we are definitely seeing rates that differ by age group.

Clinical lab data indicated 26.4% of specimens were positive for influenza. This is the third week of decrease for influenza B and the first week of decrease for influenza A.

For the season as a whole, public health labs have reported approximately equal B Victoria and A(H1N1) numbers. However, A(H1N1) has been the predominant strain in recent weeks. Most regions are seeing a similar picture, although a few regions have been predominantly B Victoria. Strain differences continue to be seen among different age groups. For the season, B viruses have been predominant in children and young adults, while influenza A viruses have been predominant in persons age 25 and older. In recent weeks, however, A viruses have been most common in all but the ages 5–24 years.

Almost 1,800 viruses have been genetically characterized and almost 300 have been antigenically characterized. The H1 and B Yamagata viruses both belong to a single genetic clade that is included in the vaccine reference viruses. All the antigenically characterized viruses are similar to the egg-grown reference virus. The majority of characterized H3 viruses belong to the 3C.2a.1 sub-clade, which is different than the 3C.3a vaccine reference virus. Despite this difference, we are still seeing that 43% of the H3 viruses that have been antigenically characterized are like the cell-grown reference virus, so some cross-protection is occurring. For B Victoria, 93% are the V1A.3 genetic subclade, while 7% are the V1A.1 subclade found in the vaccine-reference virus. Sixty-five percent (65%) of the antigenically characterized B Victoria specimens are like the cell-grown reference virus.

Very little antiviral resistance has been observed. Of the approximately 2,000 viruses tested, more than 99% were susceptible to the antiviral medications oseltamivir, zanamivir, peramivir, and baloxavir. Similar results have been found at state labs.

Outpatient influenza-like illness (ILI) activity declined from about 6% to 5.5% during the week. However, we have been at or above baseline levels for 16 weeks this season. All regions remain above baseline levels. Forty-five (45) jurisdictions reported high levels of ILI during the week.

Cumulative hospitalization rates remain moderate for the overall season, but this varies by age group. Rates are quite high in the 0–4 year old age group, and the 5–17 year old group also is higher than in recent seasons. For person 18–49, rates are higher than most recent seasons. The 50–64 and 65 and older age groups fall somewhat above recent seasons. Rates of reported pneumonia and influenza (P&I) remain low, which is consistent with higher levels of H1 transmission, which typically doesn’t impact the elderly as much.

Twenty (20) influenza-related pediatric deaths were reported during the week, bringing the 2019–2020 total for pediatric deaths to 125. Seventy percent (70%) of these deaths were associated with influenza B virus infection. All of the lineage tested viruses were B Victoria. Most of the 30% of deaths associated with influenza A virus infection were H1.

For geographic spread, fifty (50) jurisdictions reported regional or widespread activity during the week.

Preliminary in-season burden estimates indicate there have been at least 32 million flu-related illnesses, at least 310,000 flu-related hospitalizations, and at least 18,000 deaths.

Announcements – L.J Tan (IAC)
  • IMPORTANT UPDATE re: Summit Hotel Reservations – Due to a computer glitch in the hotel reservation system, many persons registered at the Westin Peachtree Plaza (the Summit/NIC hotel in Atlanta) received an INCORRECT notification that their hotel reservation had been cancelled. The hotel is aware of this issue and is working hard to get everyone reinstated. Everyone that was cancelled in error should receive a new email notification reconfirming their reservation status.
  • More Information on 2020 Summit Meeting – This year’s meeting will be held on May 18, the day prior to the opening of the National Immunization Conference (NIC). Information on registration and other pertinent details is available on the Summit website. The meeting includes a plenary keynote lunch speaker, as well as an evening Awards Banquet at which the winners of the 2020 Immunization Excellence Awards will be announced. Poster submissions will be accepted through March 15. It is acceptable to submit posters that also will be presented at NIC.
  • Summit Call Schedule – Summit calls are held each Thursday at 3 pm ET unless otherwise cancelled via an email announcement.
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