Influenza Surveillance Update – Alicia Budd (CDC)
Alicia provided an update on influenza activity reported for week 15, ending April 13, 2019. Influenza activity continues to be elevated, but it is decreasing across the country.
For the week, 11.8% of specimens sent to clinical laboratories tested positive for influenza. Influenza A (H1) remains the predominant strain reported, but the proportion of H3 reports is increasing. Looking at reports from recent weeks, all 10 regions are now H3 predominant. Region 4 is the only region that has been H3 predominant for the entire season. The amount of reported influenza B circulating viruses continues to remain very low.
During this season, 1,898 viruses have been genetically or antigenically characterized. As reported in previous weeks, all of the H1 viruses are the 6B1 clade, and 97% of the antigenically characterized H1 viruses were similar to the cell-propagated vaccine reference virus. Multiple clades and subclades of the H3 virus are co-circulating. At 67%, the 3C3a subclade is by far the predominant subclade in the U.S. this season. Sixty-seven percent (67%) of the H3s are antigenically similar to the cell-grown reference virus representing the vaccine strain. Most of the H3s that had low similarity to the cell-grown reference virus belong to clade 3C3a.
All of the Influenza B Yamagata viruses tested have belonged to the Y3 clade and are antigenically similar to the cell-grown vaccine virus. The majority of the B Victoria viruses are the V1A.1 clade, which is the same clade as the vaccine. Over 1,954 viruses have been tested for resistance to oseltamivir, peramivir, and zanamivir. A report for H1 virus specimens shows reduced or highly reduced susceptibility to oseltamivir and/or peramivir. A total of 35 H1 specimens have now been found to have reduced or highly reduced inhibition by oseltamivir and peramivir. However, more than 99% of tested viruses have been susceptible to antiviral medications.
Outpatient visits for influenza-like illness (ILI) declined to 2.4%, down from the previous week. Despite this decline, ILI activity is still elevated and has been at or above baseline nationally for more than 20 consecutive weeks. Seven of 10 surveillance regions are above their region-specific baselines. On a state level, 1 state (Rhode Island) experienced high ILI levels, 5 states reported moderate activity, 14 states and New York City, and Puerto Rico were at low activity, and 30 states and the District of Columbia reported minimal activity.
Cumulative reports to FluSurv-NET this season indicate a rate of 62.3/100,000 lab-confirmed influenza hospitalizations. Highest hospitalization rates were seen in persons >65 years at almost 206.5/100,000, followed by adults age 50–64 years at a rate of 77.8/100,000 and children 0–4 years at approximately 71.0/100,000. The percent of deaths reported due to pneumonia and influenza (P&I) was 6.6%. P&I has been relatively low for the entire season.
Five (5) influenza-associated pediatric deaths were reported to CDC during this week, bringing the total to 91 for the season.
For the geographic spread of influenza during the week, 11 states reported widespread activity. Twenty (20) states and Puerto Rico reported regional activity, and 17 states and the District of Columbia reported local activity.
For the preliminary influenza burden reports released, an estimated 36.9 – 42.4 million persons have been ill with flu, 17-19.9 million have had a medical visit, and approximately 518,000 – 630,000 persons have been hospitalized. An estimated 35,600 – 59.500 flu-related deaths have occurred.
Other Items – L.J Tan (IAC)
- 2019 Summit In-Person Meeting Information Available Online – The 2019 Summit in-person meeting will be held in Atlanta, GA on May 14–16, 2019. Information on registration is available on the 2019 National Adult and Influenza Immunization Summit webpage. (Please note that the password to register for this invitation-only meeting is available by contacting L.J Tan.) If possible, please book your room either through the onscreen “pop-up” that appears after you register or later through the email you receive after completing your registration. This not only will give you access to the “preferred rate,” it also will help the Summit meet its lodging contractual agreement with the hotel.
- Panel Discussion: Utility of Observational Real-World Evidence to Inform Vaccine and Public Health Decision-Making – Seqirus is sponsoring a dinner and panel discussion on May 14 in Atlanta. During the program, Utility of Observational Real-World Evidence to Inform Vaccine and Public Health Decision-Making, the panel will discuss the use of real-world evidence to help define how vaccine effectiveness is used to make decisions about influenza vaccines. The panel also will discuss how real-world evidence can be used to maintain confidence in the need for influenza vaccines. Panelists include: Mark Blatter, Claire Hannan, Arnold Monto, and Mitch Rothholz. While this meeting is being held in parallel with the Summit in-person meeting and at a location close to the Summit meeting, it is not associated with the Summit itself.